/** * @class Object * * Creates an object wrapper. * * The Object constructor creates an object wrapper for the given value. If the value is null or * undefined, it will create and return an empty object, otherwise, it will return an object of a type * that corresponds to the given value. * * When called in a non-constructor context, Object behaves identically. * * # Using Object given undefined and null types * * The following examples store an empty Object object in o: * var o = new Object(); * * var o = new Object(undefined); * * var o = new Object(null); * * # Using Object to create Boolean objects * * The following examples store Boolean objects in o: * * // equivalent to o = new Boolean(true); * var o = new Object(true); * * // equivalent to o = new Boolean(false); * var o = new Object(Boolean()); * * <div class="notice"> * Documentation for this class comes from <a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object">MDN</a> * and is available under <a href="http://creativecommons.org/licenses/by-sa/2.0/">Creative Commons: Attribution-Sharealike license</a>. * </div> */ /** * @method constructor * Creates new Object. * @param {Object} [value] The value to wrap. */ //Properties /** * @property prototype * Allows the addition of properties to all objects of type Object. */ //Methods /** * @method hasOwnProperty * Returns a boolean indicating whether an object contains the specified property as a direct property * of that object and not inherited through the prototype chain. * * Every object descended from `Object` inherits the `hasOwnProperty` method. This method can be used * to determine whether an object has the specified property as a direct property of that object; * unlike the `in` operator, this method does not check down the object's prototype chain. * * The following example determines whether the o object contains a property named prop: * * o = new Object(); * o.prop = 'exists'; * * function changeO() { * o.newprop = o.prop; * delete o.prop; * } * * o.hasOwnProperty('prop'); //returns true * changeO(); * o.hasOwnProperty('prop'); //returns false * * The following example differentiates between direct properties and properties inherited through the * prototype chain: * * o = new Object(); * o.prop = 'exists'; * o.hasOwnProperty('prop'); // returns true * o.hasOwnProperty('toString'); // returns false * o.hasOwnProperty('hasOwnProperty'); // returns false * * The following example shows how to iterate over the properties of an object without executing on * inherit properties. * * var buz = { * fog: 'stack' * }; * * for (var name in buz) { * if (buz.hasOwnProperty(name)) { * alert("this is fog (" + name + ") for sure. Value: " + buz[name]); * } * else { * alert(name); // toString or something else * } * } * * @param {String} prop The name of the property to test. * @return {Boolean} Returns true if object contains specified property; else * returns false. */ /** * @method isPrototypeOf * Returns a boolean indication whether the specified object is in the prototype chain of the object * this method is called upon. * * `isPrototypeOf` allows you to check whether or not an object exists within another object's * prototype chain. * * For example, consider the following prototype chain: * * function Fee() { * // . . . * } * * function Fi() { * // . . . * } * Fi.prototype = new Fee(); * * function Fo() { * // . . . * } * Fo.prototype = new Fi(); * * function Fum() { * // . . . * } * Fum.prototype = new Fo(); * * Later on down the road, if you instantiate `Fum` and need to check if `Fi`'s prototype exists * within the `Fum` prototype chain, you could do this: * * var fum = new Fum(); * . . . * * if (Fi.prototype.isPrototypeOf(fum)) { * // do something safe * } * * This, along with the `instanceof` operator particularly comes in handy if you have code that can * only function when dealing with objects descended from a specific prototype chain, e.g., to * guarantee that certain methods or properties will be present on that object. * * @param {Object} prototype an object to be tested against each link in the prototype chain of the * *object* argument * @param {Object} object the object whose prototype chain will be searched * @return {Boolean} Returns true if object is a prototype and false if not. */ /** * @method propertyIsEnumerable * Returns a boolean indicating if the internal ECMAScript DontEnum attribute is set. * * Every object has a `propertyIsEnumerable` method. This method can determine whether the specified * property in an object can be enumerated by a `for...in` loop, with the exception of properties * inherited through the prototype chain. If the object does not have the specified property, this * method returns false. * * The following example shows the use of `propertyIsEnumerable` on objects and arrays: * * var o = {}; * var a = []; * o.prop = 'is enumerable'; * a[0] = 'is enumerable'; * * o.propertyIsEnumerable('prop'); // returns true * a.propertyIsEnumerable(0); // returns true * * The following example demonstrates the enumerability of user-defined versus built-in properties: * * var a = ['is enumerable']; * * a.propertyIsEnumerable(0); // returns true * a.propertyIsEnumerable('length'); // returns false * * Math.propertyIsEnumerable('random'); // returns false * this.propertyIsEnumerable('Math'); // returns false * * Direct versus inherited properties * * var a = []; * a.propertyIsEnumerable('constructor'); // returns false * * function firstConstructor() * { * this.property = 'is not enumerable'; * } * firstConstructor.prototype.firstMethod = function () {}; * * function secondConstructor() * { * this.method = function method() { return 'is enumerable'; }; * } * * secondConstructor.prototype = new firstConstructor; * secondConstructor.prototype.constructor = secondConstructor; * * var o = new secondConstructor(); * o.arbitraryProperty = 'is enumerable'; * * o.propertyIsEnumerable('arbitraryProperty'); // returns true * o.propertyIsEnumerable('method'); // returns true * o.propertyIsEnumerable('property'); // returns false * * o.property = 'is enumerable'; * * o.propertyIsEnumerable('property'); // returns true * * // These return false as they are on the prototype which * // propertyIsEnumerable does not consider (even though the last two * // are iteratable with for-in) * o.propertyIsEnumerable('prototype'); // returns false (as of JS 1.8.1/FF3.6) * o.propertyIsEnumerable('constructor'); // returns false * o.propertyIsEnumerable('firstMethod'); // returns false * * @param {String} prop The name of the property to test. * @return {Boolean} If the object does not have the specified property, this * method returns false. */ /** * @method toLocaleString * Returns a string representing the object. This method is meant to be overridden by derived objects * for locale-specific purposes. * * `Object`'s `toLocaleString` returns the result of calling `toString`. * * This function is provided to give objects a generic `toLocaleString` method, even though not all * may use it. Currently, only `Array`, `Number`, and `Date` override `toLocaleString`. * * @return {String} Object represented as a string. */ /** * @method toString * Returns a string representation of the object. * * Every object has a `toString()` method that is automatically called when the object is to be * represented as a text value or when an object is referred to in a manner in which a string is * expected. By default, the `toString()` method is inherited by every object descended from `Object`. * If this method is not overridden in a custom object, `toString()` returns "[object type]", where * `type` is the object type. The following code illustrates this: * * var o = new Object(); * o.toString(); // returns [object Object] * * You can create a function to be called in place of the default `toString()` method. The * `toString()` method takes no arguments and should return a string. The `toString()` method you * create can be any value you want, but it will be most useful if it carries information about the * object. * * The following code defines the `Dog` object type and creates `theDog`, an object of type `Dog`: * * function Dog(name,breed,color,sex) { * this.name=name; * this.breed=breed; * this.color=color; * this.sex=sex; * } * * theDog = new Dog("Gabby","Lab","chocolate","female"); * * If you call the `toString()` method on this custom object, it returns the default value inherited * from `Object`: * * theDog.toString(); //returns [object Object] * * The following code creates and assigns `dogToString()` to override the default `toString()` method. * This function generates a string containing the name, breed, color, and sex of the object, in the * form `"property = value;"`. * * Dog.prototype.toString = function dogToString() { * var ret = "Dog " + this.name + " is a " + this.sex + " " + this.color + " " + this.breed; * return ret; * } * * With the preceding code in place, any time theDog is used in a string context, JavaScript * automatically calls the `dogToString()` function, which returns the following string: * * Dog Gabby is a female chocolate Lab * * `toString()` can be used with every object and allows you to get its class. To use the * `Object.prototype.toString()` with every object, you need to call `Function.prototype.call()` or * `Function.prototype.apply()` on it, passing the object you want to inspect as the first parameter * called `thisArg`. * * var toString = Object.prototype.toString; * * toString.call(new Date); // [object Date] * toString.call(new String); // [object String] * toString.call(Math); // [object Math] * * @return {String} Object represented as a string. */ /** * @method valueOf * Returns the primitive value of the specified object. * * JavaScript calls the `valueOf` method to convert an object to a primitive value. You rarely need to * invoke the `valueOf` method yourself; JavaScript automatically invokes it when encountering an * object where a primitive value is expected. * * By default, the `valueOf` method is inherited by every object descended from `Object`. Every built- * in core object overrides this method to return an appropriate value. If an object has no primitive * value, `valueOf` returns the object itself, which is displayed as: * * [object Object] * * You can use `valueOf` within your own code to convert a built-in object into a primitive value. * When you create a custom object, you can override `Object.valueOf` to call a custom method instead * of the default `Object` method. * * You can create a function to be called in place of the default `valueOf` method. Your function must * take no arguments. * * Suppose you have an object type `myNumberType` and you want to create a `valueOf` method for it. * The following code assigns a user-defined function to the object's valueOf method: * * myNumberType.prototype.valueOf = new Function(functionText) * * With the preceding code in place, any time an object of type `myNumberType` is used in a context * where it is to be represented as a primitive value, JavaScript automatically calls the function * defined in the preceding code. * * An object's `valueOf` method is usually invoked by JavaScript, but you can invoke it yourself as * follows: * * myNumber.valueOf() * * Note: Objects in string contexts convert via the `toString` method, which is different from * `String` objects converting to string primitives using `valueOf`. All objects have a string * conversion, if only `"[object type]"`. But many objects do not convert to number, boolean, or * function. * * @return {Object} Returns value of the object or the object itself. */ //Properties /** * @property constructor * Specifies the function that creates an object's prototype. * * Returns a reference to the Object function that created the instance's prototype. Note that the * value of this property is a reference to the function itself, not a string containing the * function's name, but it isn't read only (except for primitive Boolean, Number or String values: 1, * true, "read-only"). * * All objects inherit a `constructor` property from their `prototype`: * * o = new Object // or o = {} in JavaScript 1.2 * o.constructor == Object * a = new Array // or a = [] in JavaScript 1.2 * a.constructor == Array * n = new Number(3) * n.constructor == Number * * Even though you cannot construct most HTML objects, you can do comparisons. For example, * * document.constructor == Document * document.form3.constructor == Form * * The following example creates a prototype, `Tree`, and an object of that type, theTree. The example then displays the `constructor` property for the object `theTree`. * * function Tree(name) { * this.name = name; * } * theTree = new Tree("Redwood"); * console.log("theTree.constructor is " + theTree.constructor); * * This example displays the following output: * * theTree.constructor is function Tree(name) { * this.name = name; * } * * The following example shows how to modify constructor value of generic objects. Only true, 1 and * "test" variable constructors will not be changed. This example explains that is not always so safe * to believe in constructor function. * * function Type(){}; * var types = [ * new Array, [], * new Boolean, true, * new Date, * new Error, * new Function, function(){}, * Math, * new Number, 1, * new Object, {}, * new RegExp, /(?:)/, * new String, "test" * ]; * for(var i = 0; i < types.length; i++){ * types[i].constructor = Type; * types[i] = [types[i].constructor, types[i] instanceof Type, types[i].toString()]; * }; * alert(types.join("\n")); */