/usr/share/qt5/doc/qtqml/qjsengine.html is in qtdeclarative5-doc-html 5.9.5-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 | <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- qjsengine.cpp -->
<title>QJSEngine Class | Qt QML 5.9</title>
<link rel="stylesheet" type="text/css" href="style/offline-simple.css" />
<script type="text/javascript">
document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css");
// loading style sheet breaks anchors that were jumped to before
// so force jumping to anchor again
setTimeout(function() {
var anchor = location.hash;
// need to jump to different anchor first (e.g. none)
location.hash = "#";
setTimeout(function() {
location.hash = anchor;
}, 0);
}, 0);
</script>
</head>
<body>
<div class="header" id="qtdocheader">
<div class="main">
<div class="main-rounded">
<div class="navigationbar">
<table><tr>
<td >Qt 5.9</td><td ><a href="qtqml-index.html">Qt QML</a></td><td ><a href="qtqml-module.html">C++ Classes</a></td><td >QJSEngine</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.9.5 Reference Documentation</td>
</tr></table>
</div>
</div>
<div class="content">
<div class="line">
<div class="content mainContent">
<div class="sidebar">
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#public-types">Public Types</a></li>
<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#related-non-members">Related Non-Members</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
<li class="level2"><a href="#evaluating-scripts">Evaluating Scripts</a></li>
<li class="level2"><a href="#engine-configuration">Engine Configuration</a></li>
<li class="level2"><a href="#script-exceptions">Script Exceptions</a></li>
<li class="level2"><a href="#script-object-creation">Script Object Creation</a></li>
<li class="level2"><a href="#qobject-integration">QObject Integration</a></li>
<li class="level2"><a href="#extensions">Extensions</a></li>
</ul>
</div>
<div class="sidebar-content" id="sidebar-content"></div></div>
<h1 class="title">QJSEngine Class</h1>
<!-- $$$QJSEngine-brief -->
<p>The <a href="qjsengine.html">QJSEngine</a> class provides an environment for evaluating JavaScript code. <a href="#details">More...</a></p>
<!-- @@@QJSEngine -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QJSEngine></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += qml</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign"> Qt 5.0</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherits:</td><td class="memItemRight bottomAlign"> <a href="../qtcore/qobject.html">QObject</a></td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherited By:</td><td class="memItemRight bottomAlign"> <p><a href="qqmlengine.html">QQmlEngine</a></p>
</td></tr></table></div><ul>
<li><a href="qjsengine-members.html">List of all members, including inherited members</a></li>
<li><a href="qjsengine-obsolete.html">Obsolete members</a></li>
</ul>
<p><b>Note:</b> All functions in this class are reentrant.</p>
<a name="public-types"></a>
<h2 id="public-types">Public Types</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> enum </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#Extension-enum">Extension</a></b> { TranslationExtension, ConsoleExtension, GarbageCollectionExtension, AllExtensions }</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> flags </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#Extension-enum">Extensions</a></b></td></tr>
</table></div>
<a name="public-functions"></a>
<h2 id="public-functions">Public Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#QJSEngine">QJSEngine</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#QJSEngine-1">QJSEngine</a></b>(QObject *<i>parent</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#dtor.QJSEngine">~QJSEngine</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#collectGarbage">collectGarbage</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#evaluate">evaluate</a></b>(const QString &<i>program</i>, const QString &<i>fileName</i> = QString(), int <i>lineNumber</i> = 1)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#fromScriptValue">fromScriptValue</a></b>(const QJSValue &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#globalObject">globalObject</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#installExtensions">installExtensions</a></b>(Extensions <i>extensions</i>, const QJSValue &<i>object</i> = QJSValue())</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#newArray">newArray</a></b>(uint <i>length</i> = 0)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#newObject">newObject</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#newQMetaObject">newQMetaObject</a></b>(const QMetaObject *<i>metaObject</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#newQMetaObject-1">newQMetaObject</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#newQObject">newQObject</a></b>(QObject *<i>object</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QJSValue </td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#toScriptValue">toScriptValue</a></b>(const T &<i>value</i>)</td></tr>
</table></div>
<ul>
<li class="fn">32 public functions inherited from <a href="../qtcore/qobject.html#public-functions">QObject</a></li>
</ul>
<a name="related-non-members"></a>
<h2 id="related-non-members">Related Non-Members</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> QJSEngine *</td><td class="memItemRight bottomAlign"><b><a href="qjsengine.html#qjsEnginex">qjsEngine</a></b>(const QObject *<i>object</i>)</td></tr>
</table></div>
<h3>Additional Inherited Members</h3>
<ul>
<li class="fn">1 property inherited from <a href="../qtcore/qobject.html#properties">QObject</a></li>
<li class="fn">1 public slot inherited from <a href="../qtcore/qobject.html#public-slots">QObject</a></li>
<li class="fn">2 signals inherited from <a href="../qtcore/qobject.html#signals">QObject</a></li>
<li class="fn">1 public variable inherited from <a href="../qtcore/qobject.html#public-variables">QObject</a></li>
<li class="fn">10 static public members inherited from <a href="../qtcore/qobject.html#static-public-members">QObject</a></li>
<li class="fn">9 protected functions inherited from <a href="../qtcore/qobject.html#protected-functions">QObject</a></li>
<li class="fn">2 protected variables inherited from <a href="../qtcore/qobject.html#protected-variables">QObject</a></li>
</ul>
<a name="details"></a>
<!-- $$$QJSEngine-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qjsengine.html">QJSEngine</a> class provides an environment for evaluating JavaScript code.</p>
<a name="evaluating-scripts"></a>
<h3 >Evaluating Scripts</h3>
<p>Use <a href="qjsengine.html#evaluate">evaluate</a>() to evaluate script code.</p>
<pre class="cpp">
<span class="type"><a href="qjsengine.html#QJSEngine">QJSEngine</a></span> myEngine;
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> three <span class="operator">=</span> myEngine<span class="operator">.</span>evaluate(<span class="string">"1 + 2"</span>);
</pre>
<p><a href="qjsengine.html#evaluate">evaluate</a>() returns a <a href="qjsvalue.html">QJSValue</a> that holds the result of the evaluation. The <a href="qjsvalue.html">QJSValue</a> class provides functions for converting the result to various C++ types (e.g. <a href="qjsvalue.html#toString">QJSValue::toString</a>() and <a href="qjsvalue.html#toNumber">QJSValue::toNumber</a>()).</p>
<p>The following code snippet shows how a script function can be defined and then invoked from C++ using <a href="qjsvalue.html#call">QJSValue::call</a>():</p>
<pre class="cpp">
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> fun <span class="operator">=</span> myEngine<span class="operator">.</span>evaluate(<span class="string">"(function(a, b) { return a + b; })"</span>);
<span class="type">QJSValueList</span> args;
args <span class="operator"><</span><span class="operator"><</span> <span class="number">1</span> <span class="operator"><</span><span class="operator"><</span> <span class="number">2</span>;
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> threeAgain <span class="operator">=</span> fun<span class="operator">.</span>call(<span class="type"><a href="qjsvalue.html">QJSValue</a></span>()<span class="operator">,</span> args);
</pre>
<p>As can be seen from the above snippets, a script is provided to the engine in the form of a string. One common way of loading scripts is by reading the contents of a file and passing it to <a href="qjsengine.html#evaluate">evaluate</a>():</p>
<pre class="cpp">
<span class="type"><a href="../qtcore/qstring.html">QString</a></span> fileName <span class="operator">=</span> <span class="string">"helloworld.qs"</span>;
<span class="type"><a href="../qtcore/qfile.html">QFile</a></span> scriptFile(fileName);
<span class="keyword">if</span> (<span class="operator">!</span>scriptFile<span class="operator">.</span>open(<span class="type"><a href="../qtcore/qiodevice.html">QIODevice</a></span><span class="operator">::</span>ReadOnly))
<span class="comment">// handle error</span>
<span class="type"><a href="../qtcore/qtextstream.html">QTextStream</a></span> stream(<span class="operator">&</span>scriptFile);
<span class="type"><a href="../qtcore/qstring.html">QString</a></span> contents <span class="operator">=</span> stream<span class="operator">.</span>readAll();
scriptFile<span class="operator">.</span>close();
myEngine<span class="operator">.</span>evaluate(contents<span class="operator">,</span> fileName);
</pre>
<p>Here we pass the name of the file as the second argument to <a href="qjsengine.html#evaluate">evaluate</a>(). This does not affect evaluation in any way; the second argument is a general-purpose string that is stored in the <code>Error</code> object for debugging purposes.</p>
<a name="engine-configuration"></a>
<h3 >Engine Configuration</h3>
<p>The <a href="qjsengine.html#globalObject">globalObject</a>() function returns the <b>Global Object</b> associated with the script engine. Properties of the Global Object are accessible from any script code (i.e. they are global variables). Typically, before evaluating "user" scripts, you will want to configure a script engine by adding one or more properties to the Global Object:</p>
<pre class="cpp">
myEngine<span class="operator">.</span>globalObject()<span class="operator">.</span>setProperty(<span class="string">"myNumber"</span><span class="operator">,</span> <span class="number">123</span>);
<span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> myNumberPlusOne <span class="operator">=</span> myEngine<span class="operator">.</span>evaluate(<span class="string">"myNumber + 1"</span>);
</pre>
<p>Adding custom properties to the scripting environment is one of the standard means of providing a scripting API that is specific to your application. Usually these custom properties are objects created by the <a href="qjsengine.html#newQObject">newQObject</a>() or <a href="qjsengine.html#newObject">newObject</a>() functions.</p>
<a name="script-exceptions"></a>
<h3 >Script Exceptions</h3>
<p><a href="qjsengine.html#evaluate">evaluate</a>() can throw a script exception (e.g. due to a syntax error). If it does, then <a href="qjsengine.html#evaluate">evaluate</a>() returns the value that was thrown (typically an <code>Error</code> object). Use <a href="qjsvalue.html#isError">QJSValue::isError</a>() to check for exceptions.</p>
<p>For detailed information about the error, use <a href="qjsvalue.html#toString">QJSValue::toString</a>() to obtain an error message, and use <a href="qjsvalue.html#property">QJSValue::property</a>() to query the properties of the <code>Error</code> object. The following properties are available:</p>
<ul>
<li><code>name</code></li>
<li><code>message</code></li>
<li><code>fileName</code></li>
<li><code>lineNumber</code></li>
<li><code>stack</code></li>
</ul>
<pre class="cpp">
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> result <span class="operator">=</span> myEngine<span class="operator">.</span>evaluate(<span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>);
<span class="keyword">if</span> (result<span class="operator">.</span>isError())
<a href="../qtcore/qtglobal.html#qDebug">qDebug</a>()
<span class="operator"><</span><span class="operator"><</span> <span class="string">"Uncaught exception at line"</span>
<span class="operator"><</span><span class="operator"><</span> result<span class="operator">.</span>property(<span class="string">"lineNumber"</span>)<span class="operator">.</span>toInt()
<span class="operator"><</span><span class="operator"><</span> <span class="string">":"</span> <span class="operator"><</span><span class="operator"><</span> result<span class="operator">.</span>toString();
</pre>
<a name="script-object-creation"></a>
<h3 >Script Object Creation</h3>
<p>Use <a href="qjsengine.html#newObject">newObject</a>() to create a JavaScript object; this is the C++ equivalent of the script statement <code>new Object()</code>. You can use the object-specific functionality in <a href="qjsvalue.html">QJSValue</a> to manipulate the script object (e.g. <a href="qjsvalue.html#setProperty">QJSValue::setProperty</a>()). Similarly, use <a href="qjsengine.html#newArray">newArray</a>() to create a JavaScript array object.</p>
<a name="qobject-integration"></a>
<h3 >QObject Integration</h3>
<p>Use <a href="qjsengine.html#newQObject">newQObject</a>() to wrap a <a href="../qtcore/qobject.html">QObject</a> (or subclass) pointer. <a href="qjsengine.html#newQObject">newQObject</a>() returns a proxy script object; properties, children, and signals and slots of the <a href="../qtcore/qobject.html">QObject</a> are available as properties of the proxy object. No binding code is needed because it is done dynamically using the Qt meta object system.</p>
<pre class="cpp">
<span class="type"><a href="../qtwidgets/qpushbutton.html">QPushButton</a></span> <span class="operator">*</span>button <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="../qtwidgets/qpushbutton.html">QPushButton</a></span>;
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> scriptButton <span class="operator">=</span> myEngine<span class="operator">.</span>newQObject(button);
myEngine<span class="operator">.</span>globalObject()<span class="operator">.</span>setProperty(<span class="string">"button"</span><span class="operator">,</span> scriptButton);
myEngine<span class="operator">.</span>evaluate(<span class="string">"button.checkable = true"</span>);
<a href="../qtcore/qtglobal.html#qDebug">qDebug</a>() <span class="operator"><</span><span class="operator"><</span> scriptButton<span class="operator">.</span>property(<span class="string">"checkable"</span>)<span class="operator">.</span>toBool();
scriptButton<span class="operator">.</span>property(<span class="string">"show"</span>)<span class="operator">.</span>call(); <span class="comment">// call the show() slot</span>
</pre>
<p>Use <a href="qjsengine.html#newQMetaObject-1">newQMetaObject</a>() to wrap a <a href="../qtcore/qmetaobject.html">QMetaObject</a>; this gives you a "script representation" of a <a href="../qtcore/qobject.html">QObject</a>-based class. <a href="qjsengine.html#newQMetaObject-1">newQMetaObject</a>() returns a proxy script object; enum values of the class are available as properties of the proxy object.</p>
<p>Constructors exposed to the meta-object system (using <a href="../qtcore/qobject.html#Q_INVOKABLE">Q_INVOKABLE</a>) can be called from the script to create a new <a href="../qtcore/qobject.html">QObject</a> instance with JavaScriptOwnership. For example, given the following class definition:</p>
<pre class="cpp">
<span class="keyword">class</span> MyObject : <span class="keyword">public</span> <span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span>
{
Q_OBJECT
<span class="keyword">public</span>:
Q_INVOKABLE MyObject() {}
};
</pre>
<p>The <code>staticMetaObject</code> for the class can be exposed to JavaScript like so:</p>
<pre class="cpp">
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> jsMetaObject <span class="operator">=</span> engine<span class="operator">.</span>newQMetaObject(<span class="operator">&</span>MyObject<span class="operator">::</span>staticMetaObject);
engine<span class="operator">.</span>globalObject()<span class="operator">.</span>setProperty(<span class="string">"MyObject"</span><span class="operator">,</span> jsMetaObject);
</pre>
<p>Instances of the class can then be created in JavaScript:</p>
<pre class="cpp">
engine<span class="operator">.</span>evaluate(<span class="string">"var myObject = new MyObject()"</span>);
</pre>
<p><b>Note: </b>Currently only classes using the <a href="../qtcore/qobject.html#Q_OBJECT">Q_OBJECT</a> macro are supported; it is not possible to expose the <code>staticMetaObject</code> of a <a href="../qtcore/qobject.html#Q_GADGET">Q_GADGET</a> class to JavaScript.</p><a name="dynamic-qobject-properties"></a>
<h4 >Dynamic QObject Properties</h4>
<p>Dynamic <a href="../qtcore/qobject.html">QObject</a> properties are not supported. For example, the following code will not work:</p>
<pre class="cpp">
<span class="type"><a href="qjsengine.html#QJSEngine">QJSEngine</a></span> engine;
<span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span> <span class="operator">*</span>myQObject <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span>();
myQObject<span class="operator">-</span><span class="operator">></span>setProperty(<span class="string">"dynamicProperty"</span><span class="operator">,</span> <span class="number">3</span>);
<span class="type"><a href="qjsvalue.html">QJSValue</a></span> myScriptQObject <span class="operator">=</span> engine<span class="operator">.</span>newQObject(myQObject);
engine<span class="operator">.</span>globalObject()<span class="operator">.</span>setProperty(<span class="string">"myObject"</span><span class="operator">,</span> myScriptQObject);
<a href="../qtcore/qtglobal.html#qDebug">qDebug</a>() <span class="operator"><</span><span class="operator"><</span> engine<span class="operator">.</span>evaluate(<span class="string">"myObject.dynamicProperty"</span>)<span class="operator">.</span>toInt();
</pre>
<a name="extensions"></a>
<h3 >Extensions</h3>
<p><a href="qjsengine.html">QJSEngine</a> provides a compliant ECMAScript implementation. By default, familiar utilities like logging are not available, but they can can be installed via the <a href="qjsengine.html#installExtensions">installExtensions</a>() function.</p>
</div>
<p><b>See also </b><a href="qjsvalue.html">QJSValue</a>, <a href="qtjavascript.html">Making Applications Scriptable</a>, and <a href="qtqml-javascript-functionlist.html">List of JavaScript Objects and Functions</a>.</p>
<!-- @@@QJSEngine -->
<div class="types">
<h2>Member Type Documentation</h2>
<!-- $$$Extension$$$TranslationExtension$$$ConsoleExtension$$$GarbageCollectionExtension$$$AllExtensions -->
<h3 class="flags" id="Extension-enum"><a name="Extension-enum"></a>enum QJSEngine::<span class="name">Extension</span><br/>flags QJSEngine::<span class="name">Extensions</span></h3>
<p>This enum is used to specify extensions to be installed via <a href="qjsengine.html#installExtensions">installExtensions</a>().</p>
<div class="table"><table class="valuelist"><tr valign="top" class="odd"><th class="tblConst">Constant</th><th class="tblval">Value</th><th class="tbldscr">Description</th></tr>
<tr><td class="topAlign"><code>QJSEngine::TranslationExtension</code></td><td class="topAlign tblval"><code>0x1</code></td><td class="topAlign">Indicates that translation functions (<code>qsTr()</code>, for example) should be installed.</td></tr>
<tr><td class="topAlign"><code>QJSEngine::ConsoleExtension</code></td><td class="topAlign tblval"><code>0x2</code></td><td class="topAlign">Indicates that console functions (<code>console.log()</code>, for example) should be installed.</td></tr>
<tr><td class="topAlign"><code>QJSEngine::GarbageCollectionExtension</code></td><td class="topAlign tblval"><code>0x4</code></td><td class="topAlign">Indicates that garbage collection functions (<code>gc()</code>, for example) should be installed.</td></tr>
<tr><td class="topAlign"><code>QJSEngine::AllExtensions</code></td><td class="topAlign tblval"><code>0xffffffff</code></td><td class="topAlign">Indicates that all extension should be installed.</td></tr>
</table></div>
<p><b>TranslationExtension</b></p>
<p>The relation between script translation functions and C++ translation functions is described in the following table:</p>
<div class="table"><table class="generic">
<thead><tr class="qt-style"><th >Script Function</th><th >Corresponding C++ Function</th></tr></thead>
<tr valign="top" class="odd"><td >qsTr()</td><td ><a href="../qtcore/qobject.html#tr">QObject::tr</a>()</td></tr>
<tr valign="top" class="even"><td ><a href="../qtcore/qtglobal.html#QT_TR_NOOP">QT_TR_NOOP</a>()</td><td ><a href="../qtcore/qtglobal.html#QT_TR_NOOP">QT_TR_NOOP</a>()</td></tr>
<tr valign="top" class="odd"><td >qsTranslate()</td><td >QCoreApplication::translate()</td></tr>
<tr valign="top" class="even"><td ><a href="../qtcore/qtglobal.html#QT_TRANSLATE_NOOP">QT_TRANSLATE_NOOP</a>()</td><td ><a href="../qtcore/qtglobal.html#QT_TRANSLATE_NOOP">QT_TRANSLATE_NOOP</a>()</td></tr>
<tr valign="top" class="odd"><td >qsTrId()</td><td ><a href="../qtcore/qtglobal.html#qtTrId">qtTrId</a>()</td></tr>
<tr valign="top" class="even"><td ><a href="../qtcore/qtglobal.html#QT_TRID_NOOP">QT_TRID_NOOP</a>()</td><td ><a href="../qtcore/qtglobal.html#QT_TRID_NOOP">QT_TRID_NOOP</a>()</td></tr>
</table></div>
<p>This flag also adds an <code>arg()</code> function to the string prototype.</p>
<p>For more information, see the Internationalization with Qt documentation.</p>
<p><b>ConsoleExtension</b></p>
<p>The console object implements a subset of the <a href="https://developer.mozilla.org/en-US/docs/Web/API/Console">Console API</a>, which provides familiar logging functions, such as <code>console.log()</code>.</p>
<p>The list of functions added is as follows:</p>
<ul>
<li><code>console.assert()</code></li>
<li><code>console.debug()</code></li>
<li><code>console.exception()</code></li>
<li><code>console.info()</code></li>
<li><code>console.log()</code> (equivalent to <code>console.debug()</code>)</li>
<li><code>console.error()</code></li>
<li><code>console.time()</code></li>
<li><code>console.timeEnd()</code></li>
<li><code>console.trace()</code></li>
<li><code>console.count()</code></li>
<li><code>console.warn()</code></li>
<li><code>print()</code> (equivalent to <code>console.debug()</code>)</li>
</ul>
<p>For more information, see the Console API documentation.</p>
<p><b>GarbageCollectionExtension</b></p>
<p>The <code>gc()</code> function is equivalent to calling <a href="qjsengine.html#collectGarbage">collectGarbage</a>().</p>
<p>The Extensions type is a typedef for <a href="../qtcore/qflags.html">QFlags</a><Extension>. It stores an OR combination of Extension values.</p>
<!-- @@@Extension -->
</div>
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QJSEngine[overload1]$$$QJSEngine -->
<h3 class="fn" id="QJSEngine"><a name="QJSEngine"></a>QJSEngine::<span class="name">QJSEngine</span>()</h3>
<p>Constructs a <a href="qjsengine.html">QJSEngine</a> object.</p>
<p>The <a href="qjsengine.html#globalObject">globalObject</a>() is initialized to have properties as described in <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMA-262</a>, Section 15.1.</p>
<!-- @@@QJSEngine -->
<!-- $$$QJSEngine$$$QJSEngineQObject* -->
<h3 class="fn" id="QJSEngine-1"><a name="QJSEngine-1"></a>QJSEngine::<span class="name">QJSEngine</span>(<span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span> *<i>parent</i>)</h3>
<p>Constructs a <a href="qjsengine.html">QJSEngine</a> object with the given <i>parent</i>.</p>
<p>The <a href="qjsengine.html#globalObject">globalObject</a>() is initialized to have properties as described in <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMA-262</a>, Section 15.1.</p>
<!-- @@@QJSEngine -->
<!-- $$$~QJSEngine[overload1]$$$~QJSEngine -->
<h3 class="fn" id="dtor.QJSEngine"><a name="dtor.QJSEngine"></a><code>[virtual] </code>QJSEngine::<span class="name">~QJSEngine</span>()</h3>
<p>Destroys this <a href="qjsengine.html">QJSEngine</a>.</p>
<p>Garbage is not collected from the persistent JS heap during <a href="qjsengine.html">QJSEngine</a> destruction. If you need all memory freed, call <a href="qjsengine.html#collectGarbage">collectGarbage</a> manually right before destroying the <a href="qjsengine.html">QJSEngine</a>.</p>
<!-- @@@~QJSEngine -->
<!-- $$$collectGarbage[overload1]$$$collectGarbage -->
<h3 class="fn" id="collectGarbage"><a name="collectGarbage"></a><span class="type">void</span> QJSEngine::<span class="name">collectGarbage</span>()</h3>
<p>Runs the garbage collector.</p>
<p>The garbage collector will attempt to reclaim memory by locating and disposing of objects that are no longer reachable in the script environment.</p>
<p>Normally you don't need to call this function; the garbage collector will automatically be invoked when the <a href="qjsengine.html">QJSEngine</a> decides that it's wise to do so (i.e. when a certain number of new objects have been created). However, you can call this function to explicitly request that garbage collection should be performed as soon as possible.</p>
<!-- @@@collectGarbage -->
<!-- $$$evaluate[overload1]$$$evaluateconstQString&constQString&int -->
<h3 class="fn" id="evaluate"><a name="evaluate"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">evaluate</span>(const <span class="type"><a href="../qtcore/qstring.html">QString</a></span> &<i>program</i>, const <span class="type"><a href="../qtcore/qstring.html">QString</a></span> &<i>fileName</i> = QString(), <span class="type">int</span> <i>lineNumber</i> = 1)</h3>
<p>Evaluates <i>program</i>, using <i>lineNumber</i> as the base line number, and returns the result of the evaluation.</p>
<p>The script code will be evaluated in the context of the global object.</p>
<p>The evaluation of <i>program</i> can cause an <a href="qjsengine.html#script-exceptions">exception</a> in the engine; in this case the return value will be the exception that was thrown (typically an <code>Error</code> object; see <a href="qjsvalue.html#isError">QJSValue::isError</a>()).</p>
<p><i>lineNumber</i> is used to specify a starting line number for <i>program</i>; line number information reported by the engine that pertains to this evaluation will be based on this argument. For example, if <i>program</i> consists of two lines of code, and the statement on the second line causes a script exception, the exception line number would be <i>lineNumber</i> plus one. When no starting line number is specified, line numbers will be 1-based.</p>
<p><i>fileName</i> is used for error reporting. For example, in error objects the file name is accessible through the "fileName" property if it is provided with this function.</p>
<p><b>Note: </b>If an exception was thrown and the exception value is not an Error instance (i.e., <a href="qjsvalue.html#isError">QJSValue::isError</a>() returns <code>false</code>), the exception value will still be returned, but there is currently no API for detecting that an exception did occur in this case.</p><!-- @@@evaluate -->
<!-- $$$fromScriptValue[overload1]$$$fromScriptValueconstQJSValue& -->
<h3 class="fn" id="fromScriptValue"><a name="fromScriptValue"></a><span class="type">T</span> QJSEngine::<span class="name">fromScriptValue</span>(const <span class="type"><a href="qjsvalue.html">QJSValue</a></span> &<i>value</i>)</h3>
<p>Returns the given <i>value</i> converted to the template type <code>T</code>.</p>
<p><b>See also </b><a href="qjsengine.html#toScriptValue">toScriptValue</a>().</p>
<!-- @@@fromScriptValue -->
<!-- $$$globalObject[overload1]$$$globalObject -->
<h3 class="fn" id="globalObject"><a name="globalObject"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">globalObject</span>() const</h3>
<p>Returns this engine's Global Object.</p>
<p>By default, the Global Object contains the built-in objects that are part of <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMA-262</a>, such as Math, Date and String. Additionally, you can set properties of the Global Object to make your own extensions available to all script code. Non-local variables in script code will be created as properties of the Global Object, as well as local variables in global code.</p>
<!-- @@@globalObject -->
<!-- $$$installExtensions[overload1]$$$installExtensionsExtensionsconstQJSValue& -->
<h3 class="fn" id="installExtensions"><a name="installExtensions"></a><span class="type">void</span> QJSEngine::<span class="name">installExtensions</span>(<span class="type"><a href="qjsengine.html#Extension-enum">Extensions</a></span> <i>extensions</i>, const <span class="type"><a href="qjsvalue.html">QJSValue</a></span> &<i>object</i> = QJSValue())</h3>
<p>Installs JavaScript <i>extensions</i> to add functionality that is not available in a standard ECMAScript implementation.</p>
<p>The extensions are installed on the given <i>object</i>, or on the <a href="qjsengine.html#globalObject">Global Object</a> if no object is specified.</p>
<p>Several extensions can be installed at once by <code>OR</code>-ing the enum values:</p>
<pre class="cpp">
installExtensions(<span class="type"><a href="qjsengine.html#QJSEngine">QJSEngine</a></span><span class="operator">::</span>TranslationExtension <span class="operator">|</span> <span class="type"><a href="qjsengine.html#QJSEngine">QJSEngine</a></span><span class="operator">::</span>ConsoleExtension);
</pre>
<p>This function was introduced in Qt 5.6.</p>
<p><b>See also </b><a href="qjsengine.html#Extension-enum">Extension</a>.</p>
<!-- @@@installExtensions -->
<!-- $$$newArray[overload1]$$$newArrayuint -->
<h3 class="fn" id="newArray"><a name="newArray"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">newArray</span>(<span class="type"><a href="../qtcore/qtglobal.html#uint-typedef">uint</a></span> <i>length</i> = 0)</h3>
<p>Creates a JavaScript object of class Array with the given <i>length</i>.</p>
<p><b>See also </b><a href="qjsengine.html#newObject">newObject</a>().</p>
<!-- @@@newArray -->
<!-- $$$newObject[overload1]$$$newObject -->
<h3 class="fn" id="newObject"><a name="newObject"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">newObject</span>()</h3>
<p>Creates a JavaScript object of class Object.</p>
<p>The prototype of the created object will be the Object prototype object.</p>
<p><b>See also </b><a href="qjsengine.html#newArray">newArray</a>() and <a href="qjsvalue.html#setProperty">QJSValue::setProperty</a>().</p>
<!-- @@@newObject -->
<!-- $$$newQMetaObject[overload1]$$$newQMetaObjectconstQMetaObject* -->
<h3 class="fn" id="newQMetaObject"><a name="newQMetaObject"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">newQMetaObject</span>(const <span class="type"><a href="../qtcore/qmetaobject.html">QMetaObject</a></span> *<i>metaObject</i>)</h3>
<p>Creates a JavaScript object that wraps the given <a href="../qtcore/qmetaobject.html">QMetaObject</a> The <i>metaObject</i> must outlive the script engine. It is recommended to only use this method with static metaobjects.</p>
<p>When called as a constructor, a new instance of the class will be created. Only constructors exposed by <a href="../qtcore/qobject.html#Q_INVOKABLE">Q_INVOKABLE</a> will be visible from the script engine.</p>
<p>This function was introduced in Qt 5.8.</p>
<p><b>See also </b><a href="qjsengine.html#newQObject">newQObject</a>() and <a href="qjsengine.html#qobject-integration">QObject Integration</a>.</p>
<!-- @@@newQMetaObject -->
<!-- $$$newQMetaObject$$$newQMetaObject -->
<h3 class="fn" id="newQMetaObject-1"><a name="newQMetaObject-1"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">newQMetaObject</span>()</h3>
<p>Creates a JavaScript object that wraps the static <a href="../qtcore/qmetaobject.html">QMetaObject</a> associated with class <code>T</code>.</p>
<p>This function was introduced in Qt 5.8.</p>
<p><b>See also </b><a href="qjsengine.html#newQObject">newQObject</a>() and <a href="qjsengine.html#qobject-integration">QObject Integration</a>.</p>
<!-- @@@newQMetaObject -->
<!-- $$$newQObject[overload1]$$$newQObjectQObject* -->
<h3 class="fn" id="newQObject"><a name="newQObject"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">newQObject</span>(<span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span> *<i>object</i>)</h3>
<p>Creates a JavaScript object that wraps the given <a href="../qtcore/qobject.html">QObject</a> <i>object</i>, using JavaScriptOwnership.</p>
<p>Signals and slots, properties and children of <i>object</i> are available as properties of the created <a href="qjsvalue.html">QJSValue</a>.</p>
<p>If <i>object</i> is a null pointer, this function returns a null value.</p>
<p>If a default prototype has been registered for the <i>object</i>'s class (or its superclass, recursively), the prototype of the new script object will be set to be that default prototype.</p>
<p>If the given <i>object</i> is deleted outside of the engine's control, any attempt to access the deleted <a href="../qtcore/qobject.html">QObject</a>'s members through the JavaScript wrapper object (either by script code or C++) will result in a <a href="qjsengine.html#script-exceptions">script exception</a>.</p>
<p><b>See also </b><a href="qjsvalue.html#toQObject">QJSValue::toQObject</a>().</p>
<!-- @@@newQObject -->
<!-- $$$toScriptValue[overload1]$$$toScriptValueconstT& -->
<h3 class="fn" id="toScriptValue"><a name="toScriptValue"></a><span class="type"><a href="qjsvalue.html">QJSValue</a></span> QJSEngine::<span class="name">toScriptValue</span>(const <span class="type">T</span> &<i>value</i>)</h3>
<p>Creates a <a href="qjsvalue.html">QJSValue</a> with the given <i>value</i>.</p>
<p><b>See also </b><a href="qjsengine.html#fromScriptValue">fromScriptValue</a>().</p>
<!-- @@@toScriptValue -->
</div>
<div class="relnonmem">
<h2>Related Non-Members</h2>
<!-- $$$qjsEngine[overload1]$$$qjsEngineconstQObject* -->
<h3 class="fn" id="qjsEnginex"><a name="qjsEnginex"></a><span class="type"><a href="qjsengine.html#QJSEngine">QJSEngine</a></span> *<span class="name">qjsEngine</span>(const <span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span> *<i>object</i>)</h3>
<p>Returns the <a href="qjsengine.html">QJSEngine</a> associated with <i>object</i>, if any.</p>
<p>This function is useful if you have exposed a <a href="../qtcore/qobject.html">QObject</a> to the JavaScript environment and later in your program would like to regain access. It does not require you to keep the wrapper around that was returned from <a href="qjsengine.html#newQObject">QJSEngine::newQObject</a>().</p>
<p>This function was introduced in Qt 5.5.</p>
<!-- @@@qjsEngine -->
</div>
</div>
</div>
</div>
</div>
</div>
<div class="footer">
<p>
<acronym title="Copyright">©</acronym> 2017 The Qt Company Ltd.
Documentation contributions included herein are the copyrights of
their respective owners.<br> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property
of their respective owners. </p>
</div>
</body>
</html>
|