在Javascript函数中var和this之间的区别？ [英] Difference between var and this in Javascript functions?

问题描述

var tools = {};

tools.triangle = function() {
    var originX = 0;
    var originY = 0;
}

 

var tools = {};

tools.triangle = function() {
    this.originX = 0;
    this.originY = 0;
}

这两个代码块之间是否有任何差异？很抱歉，如果之前已经询问过。

Are there any differences between these two code blocks? Sorry if this has been asked before.

推荐答案

var 创建一个本地变量 tools.triangle 。变量 originX 和 originY 无法与 tools.triangle 。 此是指向您正在处理的当前对象的指针。第二个示例可用于通过 new tools.triangle（）; 为对象提供属性。如果你不使用 new ，只需使用 tools.triangle（）; ， this 将指向全局对象，即窗口对象。您可以使用函数方法更改此指向的对象 call（）; 和 apply（）; 如下：

var creates a local variable within tools.triangle. The variables originX and originY cannot be interacted with outside of tools.triangle. this is a pointer to the current object you are dealing with. The second example can be used to give properties to an object by doing new tools.triangle();. If you do not use new and just use tools.triangle();, this will point the global object which is the window object. You can change the object to which this points by using the function methods call(); and apply(); like this:

var myObj = {};

tools.triangle.call( myObj );

// "this" in tools.triangle now points to myObj
// myObj now has the properties originX and originY

重要的是要知道这个可以引用任何对象，以及未定义或 null 在ES5严格模式下。

It is important to know that this can reference any object, as well as be undefined or null in ES5 strict mode.

您可以找到更多信息 here 。

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