Function

概述

Function 构造器创建一个新的Function 对象. 在JavaScript中每个函数(function)实际是一个Function对象.

构造器

new Function ([arg1[, arg2[, ...argN]],] functionBody)

参数

参数1, 参数2, ... 参数N: 被函数使用的参数的名称必须是合法命名的。参数名称是一个有效的JavaScript标识符的字符串，或者一个用逗号分隔的有效字符串的列表;例如“×”，“theValue”，或“A，B”。
函数体: 一个含有包括函数定义的JavaScript语句的字符串。

描述

使用Function构造器生成的Function对象是在函数创建时被解析的。这比你使用函数声明(function)并在你的代码中调用低效，因为使用函数语句声明的function是跟其他语句一起解析的。

所有被传递到构造函数中的参数，都将被视为将被创建的函数的参数，并且是相同的标示符名称和传递顺序。

Note: Functions created with the Function constructor do not create closures to their creation contexts; they always are created in the global scope. When running them, they will only be able to access their own local variables and global ones, not the ones from the scope in which the Function constructor was called. This is different from using eval with code for a function expression.

Invoking the Function constructor as a function (without using the new operator) has the same effect as invoking it as a constructor.

Properties and Methods of `Function`

The global Function object has no methods or properties of its own, however, since it is a function itself it does inherit some methods and properties through the prototype chain from Function.prototype.

`Function` prototype object

Properties

Function.arguments: An array corresponding to the arguments passed to a function. This is deprecated as property of Function, use the arguments object available within the function instead.
~~Function.arity~~: ~~Used to specifiy the number of arguments expected by the function, but has been removed. Use the length property instead.~~
Function.caller: Specifies the function that invoked the currently executing function.
Function.length: Specifies the number of arguments expected by the function.
Function.name: The name of the function.
Function.displayName: The display name of the function.
Function.prototype.constructor: Specifies the function that creates an object's prototype. See Object.constructor for more details.

Properties inherited from Object:

__parent__, __proto__

Methods

Function.prototype.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.
Function.prototype.bind(): Creates a new function which, when called, itself calls this function in the context of the provided value, with a given sequence of arguments preceding any provided when the new function was called.
Function.prototype.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.
Function.prototype.isGenerator(): Returns true if the function is a generator; otherwise returns false.
Function.prototype.toSource(): Returns a string representing the source code of the function. Overrides the Object.toSource method.
Function.prototype.toString(): Returns a string representing the source code of the function. Overrides the Object.toString method.

Methods inherited from Object:

__defineGetter__, __defineSetter__, hasOwnProperty, isPrototypeOf, __lookupGetter__, __lookupSetter__, __noSuchMethod__, propertyIsEnumerable, toLocaleString, unwatch, valueOf, watch

`Function` instances

Function instances inherit methods and properties from Function.prototype. As with all constructors, you can change the constructor's prototype object to make changes to all Function instances.

Examples

Example: 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".

Example: A recursive shortcut to massively modify the DOM

Creating functions with the Function constructor is one of the ways to dynamically create an indeterminate number of new objects with some executable code into the global scope from a function. The following example (a recursive shortcut to massively modify the DOM) is impossible without the invocation of the Function constructor for each new query if you want to avoid closures.

<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>MDN Example - a recursive shortcut to massively modify the DOM</title>
<script type="text/javascript">
var domQuery = (function() {
  var aDOMFunc = [
        Element.prototype.removeAttribute,
        Element.prototype.setAttribute,
        CSSStyleDeclaration.prototype.removeProperty,
        CSSStyleDeclaration.prototype.setProperty
      ];

  function setSomething (bStyle, sProp, sVal) {
    var  bSet = Boolean(sVal), fAction = aDOMFunc[bSet | bStyle << 1],
         aArgs = Array.prototype.slice.call(arguments, 1, bSet ? 3 : 2),
         aNodeList = bStyle ? this.cssNodes : this.nodes;

    if (bSet && bStyle) { aArgs.push(""); }
    for (
      var nItem = 0, nLen = this.nodes.length;
      nItem < nLen;
      fAction.apply(aNodeList[nItem++], aArgs)
    );
    this.follow = setSomething.caller;
    return this;
  }

  function setStyles (sProp, sVal) { return setSomething.call(this, true, sProp, sVal); }
  function setAttribs (sProp, sVal) { return setSomething.call(this, false, sProp, sVal); }
  function getSelectors () { return this.selectors; };
  function getNodes () { return this.nodes; };

  return (function (sSelectors) {
    var oQuery = new Function("return arguments.callee.follow.apply(arguments.callee, arguments);");
    oQuery.selectors = sSelectors;
    oQuery.nodes = document.querySelectorAll(sSelectors);
    oQuery.cssNodes = Array.prototype.map.call(oQuery.nodes, function (oInlineCSS) { return oInlineCSS.style; });
    oQuery.attributes = setAttribs;
    oQuery.inlineStyle = setStyles;
    oQuery.follow = getNodes;
    oQuery.toString = getSelectors;
    oQuery.valueOf = getNodes;
    return oQuery;
  });
})();
</script>
</head>

<body>

<div class="testClass">Lorem ipsum</div>
<p>Some text</p>
<div class="testClass">dolor sit amet</div>

<script type="text/javascript">
  domQuery(".testClass").attributes("lang", "en")("title", "Risus abundat in ore stultorum")
  .inlineStyle("background-color", "black")("color", "white")("width", "100px")("height", "50px");
</script>
</body>

</html>

Specifications

Specification	Status	Comment
ECMAScript 1st Edition. Implemented in JavaScript 1.0	Standard	Initial definition.
ECMAScript 5.1 (ECMA-262) Function	Standard
ECMAScript 6 (ECMA-262) Function	Draft

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic support	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)

Feature	Android	Chrome for Android	Firefox Mobile (Gecko)	IE Mobile	Opera Mobile	Safari Mobile
Basic support	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)

Function

概述

构造器

参数

描述

Properties and Methods of `Function`

`Function` prototype object

Properties

Methods

`Function` instances

Examples

Example: Specifying arguments with the `Function` constructor

Example: A recursive shortcut to massively modify the DOM

Specifications

Browser compatibility

See also

文档标签和贡献者

Function

概述

构造器

参数

描述

Properties and Methods of Function

Function prototype object

Properties

Methods

Function instances

Examples

Example: Specifying arguments with the Function constructor

Example: A recursive shortcut to massively modify the DOM

Specifications

Browser compatibility

See also

文档标签和贡献者

Properties and Methods of `Function`

`Function` prototype object

`Function` instances

Example: Specifying arguments with the `Function` constructor