如何在匿名函数调用中获取外循环索引? [英] How to get outer loop index inside anonymous function call?

问题描述

我有以下 javascript 代码:

I have the following javascript code :

var Person = [['John', 0, 0, 0],['Chris', 1, 0, 0]];
for (i = 0; i < Person.length; i++ )
{
    someObj.myMethod(Person[i][0], function (object) {
        console.log(i); //this prints 2, I want 0 and 1 as per the loop

        //here I want to access other members of Person[i] array, like Person[i][1], Person[i][2] and Person[i][3]
        //but these console.log() print 'undefined' because i = 2 !!
        console.log(Person[i][1]);
        console.log(Person[i][2]);
        console.log(Person[i][3]);
    });
}

在 myMethod() 中调用的匿名函数中，i 的值为 '2'.请建议如何在 for 循环的第一个循环中获得 i = 0，然后在第二个循环中获得 1.

Inside the anonymous function called inside my myMethod(), value of i is '2'. Please suggest how to get i = 0 in first cycle of for loop and then 1 in the second loop.

推荐答案

使用闭包，这是一个解决方案:

With a closure, this a solution:

var Person = [['John', 0, 0, 0],['Chris', 1, 0, 0]];
for (x = 0; x < Person.length; x++ )
{
    (function(i){   //We add a closure
        someObj.myMethod(Person[i][0], function (object) {
          console.log(i);
          console.log(Person[i][1]);
          console.log(Person[i][2]);
          console.log(Person[i][3]);
      });
    })(x);      //Call the closure function with the value of the counter
}

我将原始计数器更改为 x 以使其更易于理解(因此您不要将该变量与原始 i 混淆)，但如果它保持命名为 >i，它也能用.

I changed the original counter to x to make it more understandable (so you dont confuse that variable with the original i), but if it keeps named also i, it will work, too.

这样，每个循环周期都有自己的变量 x(不共享)，所以它不会被 for 循环覆盖，这导致了问题(i 已共享) :)

This way, each loop cycle has it's own variable x (not shared), so it doesn't get overwritten by the for loop, which was causing the problem (i was shared) :)

干杯

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