Returns the unique identifier generated by the browser for the object

uniqueID.js

/**
 * @file Returns the unique identifier generated by the browser for the object.
 *       The uniqueID property of the document works as an identifier generator in Internet Explorer.
 *       Each time when the value of this uniqueID property is retrieved, the browser generates
 *       a new unique identifier and returns it.
 *       HTML elements also support the uniqueID property. The first time when the value of any of these
 *       properties is retrieved, the browser generates a new identifier for the element.
 * @author Renaat De Muynck <renaat.demuynck@gmail.com>
 */

(function () {
    
    'use strict';
    
    var nextID = 1;
    
    if (Document.prototype.hasOwnProperty('uniqueID')) {
        return;
    }
    
    console.info('"document.uniqueID" not implemented; creating shim');
    
    // define a property on the document that will generate a unique id each time it is called
    Object.defineProperty(Document.prototype, 'uniqueID', {
        get: function () {
            return nextID++;
        },
        enumerable: false,
        configurable: false
    });
    
    // define a property on the element that will return a unique id the first time it is called
    Object.defineProperty(Element.prototype, 'uniqueID', {
        get: function () {
            // redefine the property so that the generator will not be called again
            Object.defineProperty(this, 'uniqueID', {
                value: document.uniqueID,
                writable: false,
                enumerable: false,
                configurable: false
            });
            
            return this.uniqueID;
        },
        enumerable: false,
        configurable: true
    });
    
}());