javascript:在函数(){}中使用当前的for循环计数器值?

2022-01-20 00:00:00 复制 for-loop scope javascript anonymous-function

在我想这样做的网站上:(简化)

on a website i want to do this: (simplified)

myHandlers = new Array();
for(var i = 0; i < 7; i++) {
  myHandlers.push(new Handler({
    handlerName: 'myHandler'+i, // works, e.g. ->myHandler1, 2, 3 etc.
    handlerFunc: function(bla) { /*...*/ alert(i); } // doesn't work,all return 7
  }
}

我可以将计数器设置为我的 Handler 的另一个属性(它将复制当前值)并在我的函数中使用它，但我想，还有一种方法可以实际复制这个值，不是吗?

I could set the counter as another attribute of my Handler (which would copy the current value) and use it inside my function, but I guess, there is also a way to actually copy this value, no?

推荐答案

当调用handlerFunc时，函数内部的i指的是ifor 循环的代码>.但是那个 i 可能不再具有相同的值了.

When handlerFunc is called, the i inside the function refers to the i of the for loop. But that i does probably not have the same value any more.

使用闭包将 i 的当前值绑定到匿名函数的范围内:

Use a closure to bind the current value of i in the scope of an anonymous function:

handlerFunc: (function(i) { return function(bla) { /*...*/ alert(i); }; })(i)

这里使用了一个匿名函数 (function(i) { … })(i) 并立即调用.该函数将 for 循环的 i 的值绑定到本地 i.该 i 然后独立于 for 循环的 i.

Here an anonymous function (function(i) { … })(i) is used and called immediately. This function binds the value of i of the for loop to the local i. That i is then independent from the i of the for loop.

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