Function.html
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<pre class="prettyprint lang-js"><span id='Function'>/**
</span> * @class Function
*
* Every function in JavaScript is actually a `Function` object.
*
* `Function` objects created with the `Function` constructor are parsed when the
* function is created. This is less efficient than declaring a function and
* calling it within your code, because functions declared with the function
* statement are parsed with the rest of the code.
*
* All arguments passed to the function are treated as the names of the
* identifiers of the parameters in the function to be created, in the order in
* which they are passed.
*
* Invoking the `Function` constructor as a function (without using the `new`
* operator) has the same effect as invoking it as a constructor.
*
* # Specifying arguments with the `Function` constructor
*
* The following code creates a `Function` object that takes two arguments.
*
* // Example can be run directly in your JavaScript console
*
* // Create a function that takes two arguments and returns the sum of those
* arguments
* var adder = new Function("a", "b", "return a + b");
*
* // Call the function
* adder(2, 6);
* // > 8
*
* The arguments "a" and "b" are formal argument names that are used in the
* function body, "return a + b".
*
* <div class="notice">
* Documentation for this class comes from <a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function">MDN</a>
* and is available under <a href="http://creativecommons.org/licenses/by-sa/2.0/">Creative Commons: Attribution-Sharealike license</a>.
* </div>
*/
<span id='Function-method-constructor'>/**
</span> * @method constructor
* Creates new Function object.
*
* @param {String...} args
* Names to be used by the function as formal argument names. Each must be a
* string that corresponds to a valid JavaScript identifier or a list of such
* strings separated with a comma; for example "`x`", "`theValue`", or "`a,b`".
* @param {String} functionBody
* A string containing the JavaScript statements comprising the function
* definition.
*/
// Properties
<span id='Function-property-length'>/**
</span> * @property {Number} length
* Specifies the number of arguments expected by the function.
*/
//Methods
<span id='Function-method-apply'>/**
</span> * @method apply
* Applies the method of another object in the context of a different object (the
* calling object); arguments can be passed as an Array object.
*
* You can assign a different this object when calling an existing function. `this` refers to the
* current object, the calling object. With `apply`, you can write a method once and then inherit it
* in another object, without having to rewrite the method for the new object.
*
* `apply` is very similar to call, except for the type of arguments it supports. You can use an
* arguments array instead of a named set of parameters. With apply, you can use an array literal, for
* example, `fun.apply(this, ['eat', 'bananas'])`, or an Array object, for example, `fun.apply(this,
* new Array('eat', 'bananas'))`.
*
* You can also use arguments for the `argsArray` parameter. `arguments` is a local variable of a
* function. It can be used for all unspecified arguments of the called object. Thus, you do not have
* to know the arguments of the called object when you use the `apply` method. You can use arguments
* to pass all the arguments to the called object. The called object is then responsible for handling
* the arguments.
*
* Since ECMAScript 5th Edition you can also use any kind of object which is array like, so in
* practice this means it's going to have a property length and integer properties in the range
* `[0...length)`. As an example you can now use a NodeList or a own custom object like `{'length': 2,
* '0': 'eat', '1': 'bananas'}`.
*
* You can use `apply` to chain constructors for an object, similar to Java. In the following example,
* the constructor for the `Product` object is defined with two parameters, `name` and `value`. Two
* other functions `Food` and `Toy` invoke `Product` passing `this` and `arguments`. `Product`
* initializes the properties `name` and `price`, both specialized functions define the category. In
* this example, the `arguments` object is fully passed to the product constructor and corresponds to
* the two defined parameters.
*
* function Product(name, price) {
* this.name = name;
* this.price = price;
*
* if (price < 0)
* throw RangeError('Cannot create product "' + name + '" with a negative price');
* return this;
* }
*
* function Food(name, price) {
* Product.apply(this, arguments);
* this.category = 'food';
* }
* Food.prototype = new Product();
*
* function Toy(name, price) {
* Product.apply(this, arguments);
* this.category = 'toy';
* }
* Toy.prototype = new Product();
*
* var cheese = new Food('feta', 5);
* var fun = new Toy('robot', 40);
*
* Clever usage of `apply` allows you to use built-ins functions for some tasks that otherwise
* probably would have been written by looping over the array values. As an example here we are going
* to use Math.max/Math.min to find out the maximum/minimum value in an array.
*
* //min/max number in an array
* var numbers = [5, 6, 2, 3, 7];
*
* //using Math.min/Math.max apply
* var max = Math.max.apply(null, numbers); // This about equal to Math.max(numbers[0], ...) or
* // Math.max(5, 6, ..)
* var min = Math.min.apply(null, numbers);
*
* //vs. simple loop based algorithm
* max = -Infinity, min = +Infinity;
*
* for (var i = 0; i < numbers.length; i++) {
* if (numbers[i] > max)
* max = numbers[i];
* if (numbers[i] < min)
* min = numbers[i];
* }
*
* But beware: in using `apply` this way, you run the risk of exceeding the JavaScript engine's
* argument length limit. The consequences of applying a function with too many arguments (think more
* than tens of thousands of arguments) vary across engines, because the limit (indeed even the nature
* of any excessively-large-stack behavior) is unspecified. Some engines will throw an exception. More
* perniciously, others will arbitrarily limit the number of arguments actually passed to the applied
* function. (To illustrate this latter case: if such an engine had a limit of four arguments [actual
* limits are of course significantly higher], it would be as if the arguments 5, 6, 2, 3 had been
* passed to apply in the examples above, rather than the full array.) If your value array might grow
* into the tens of thousands, use a hybrid strategy: apply your function to chunks of the array at a
* time:
*
* function minOfArray(arr)
* {
* var min = Infinity;
* var QUANTUM = 32768;
* for (var i = 0, len = arr.length; i < len; i += QUANTUM)
* {
* var submin = Math.min.apply(null, numbers.slice(i, Math.min(i + QUANTUM, len)));
* min = Math.min(submin, min);
* }
* return min;
* }
*
* var min = minOfArray([5, 6, 2, 3, 7]);
*
* @param {Object} thisArg The value of this provided for the call to fun. Note that this may not be
* the actual value seen by the method: if the method is a function in non-strict mode code, null and
* undefined will be replaced with the global object, and primitive values will be boxed.
* @param {Array} argsArray An array like object, specifying the arguments with which fun should be
* called, or null or undefined if no arguments should be provided to the function.
* @return {Object} Returns what the function returns.
*/
<span id='Function-method-call'>/**
</span> * @method call
* Calls (executes) a method of another object in the context of a different
* object (the calling object); arguments can be passed as they are.
*
* You can assign a different this object when calling an existing function. `this` refers to the
* current object, the calling object.
*
* With `call`, you can write a method once and then inherit it in another object, without having to
* rewrite the method for the new object.
*
* You can use call to chain constructors for an object, similar to Java. In the following example,
* the constructor for the product object is defined with two parameters, name and value. Another
* object, `prod_dept`, initializes its unique variable (`dept`) and calls the constructor for
* `product` in its constructor to initialize the other variables.
*
* function Product(name, price) {
* this.name = name;
* this.price = price;
*
* if (price < 0)
* throw RangeError('Cannot create product "' + name + '" with a negative price');
* return this;
* }
*
* function Food(name, price) {
* Product.call(this, name, price);
* this.category = 'food';
* }
* Food.prototype = new Product();
*
* function Toy(name, price) {
* Product.call(this, name, price);
* this.category = 'toy';
* }
* Toy.prototype = new Product();
*
* var cheese = new Food('feta', 5);
* var fun = new Toy('robot', 40);
*
* In this purely constructed example, we create anonymous function and use `call` to invoke it on
* every object in an array. The main purpose of the anonymous function here is to add a print
* function to every object, which is able to print the right index of the object in the array.
* Passing the object as `this` value was not strictly necessary, but is done for explanatory purpose.
*
* var animals = [
* {species: 'Lion', name: 'King'},
* {species: 'Whale', name: 'Fail'}
* ];
*
* for (var i = 0; i < animals.length; i++) {
* (function (i) {
* this.print = function () {
* console.log('#' + i + ' ' + this.species + ': ' + this.name);
* }
* }).call(animals[i], i);
* }
*
* @param {Object} thisArg The value of this provided for the call to `fun`.Note that this may not be
* the actual value seen by the method: if the method is a function in non-strict mode code, `null`
* and `undefined` will be replaced with the global object, and primitive values will be boxed.
* @param {Object...} args Arguments for the object.
* @return {Object} Returns what the function returns.
*/
<span id='Function-method-toString'>/**
</span> * @method toString
* Returns a string representing the source code of the function. Overrides the
* `Object.toString` method.
*
* The {@link Function} object overrides the `toString` method of the Object object; it does
* not inherit Object.toString. For `Function` objects, the `toString` method returns a string
* representation of the object.
*
* JavaScript calls the `toString` method automatically when a `Function` is to be represented as a
* text value or when a Function is referred to in a string concatenation.
*
* For `Function` objects, the built-in `toString` method decompiles the function back into the
* JavaScript source that defines the function. This string includes the `function` keyword, the
* argument list, curly braces, and function body.
*
* @return {String} The function as a string.
*/</pre>
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