This file is indexed.

/usr/lib/nodejs/es5-ext/number/is-number.js is in node-es5-ext 0.10.30-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

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"use strict";

var objToString = Object.prototype.toString, id = objToString.call(1);

module.exports = function (value) {
	return (
		typeof value === "number" ||
		(value instanceof Number || (typeof value === "object" && objToString.call(value) === id))
	);
};