设置“this”容易变? [英] Set "this" variable easily?
问题描述
我对Javascript有很好的理解,除了我找不到设置this变量的好方法。考虑:
I have a pretty good understanding of Javascript, except that I can't figure out a nice way to set the "this" variable. Consider:
var myFunction = function(){
alert(this.foo_variable);
}
var someObj = document.body; //using body as example object
someObj.foo_variable = "hi"; //set foo_variable so it alerts
var old_fn = someObj.fn; //store old value
someObj.fn = myFunction; //bind to someObj so "this" keyword works
someObj.fn();
someObj.fn = old_fn; //restore old value
有没有办法在没有最后4行的情况下执行此操作?这很烦人......我试过绑定一个匿名函数,我认为这个函数漂亮而且聪明,但无济于事:
Is there a way to do this without the last 4 lines? It's rather annoying... I've tried binding an anonymous function, which I thought was beautiful and clever, but to no avail:
var myFunction = function(){
alert(this.foo_variable);
}
var someObj = document.body; //using body as example object
someObj.foo_variable = "hi"; //set foo_variable so it alerts
someObj.(function(){ fn(); })(); //fail.
显然,将变量传递给myFunction是一个选项...但这不是这个问题的重点。
Obviously, passing the variable into myFunction is an option... but that's not the point of this question.
谢谢。
推荐答案
为所有人定义了两种方法JavaScript中的函数, 调用()
, 应用()
。函数语法如下:
There are two methods defined for all functions in JavaScript, call()
, and apply()
. The function syntax looks like:
call( /* object */, /* arguments... */ );
apply(/* object */, /* arguments[] */);
这些函数的作用是调用它们被调用的函数,赋值对象参数 this 。
What these functions do is call the function they were invoked on, assigning the value of the object parameter to this.
var myFunction = function(){
alert(this.foo_variable);
}
myFunction.call( document.body );
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