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问题描述

我发现非常有用的函数 reduce(),我正在使用它,但我不确定我是否理解它。任何人都可以帮我理解这个功能吗?

I found very useful function reduce(), and I'm using it, but I'm not sure if I understand it properly. Can any one help me to understand this function?

示例:

var arr = [1,2,3,4,5,6];
arr.reduce(function(p,n){
 return p+n;
},0);
// Output 21

这是我的理解:减少( )循环遍历数组的每个元素并返回前一个+当前值。防爆。 0 + 1,1 + 2等。在这种情况下,此函数将返回[0] - 返回1; [1] - 返回3; [2] - 返回5,[3] - 返回7,[4] - 返回9,[5] - 返回11.下一步是什么?为什么它给出结果21?

This is my understanding: Reduce() loop through every element of the array and returning previous + current value . Ex. 0+1, 1+2 etc. In this case this function will return [0] - return 1; [1] - return 3; [2] - return 5, [3] - return 7, [4] - return 9, [5] - return 11. What next? Why does it give the result 21?

推荐答案

取自, arr.reduce()将减少数组到一个值,由回调指定。在您的情况下,它基本上将数组的元素相加。
步骤:

Taken from here, arr.reduce() will reduce the array to a value, specified by the callback. In your case, it will basically sum the elements of the array. Steps:


  • 0,1上的调用函数(0是传递给 .reduce的初始值()作为第二个参数。返回和0和1,即1。

  • 对前一个结果(即1)和下一个数组元素的调用函数这将返回1和2的总和,即3

  • 重复直到最后一个元素,总计为21

  • Call function on 0,1 ( 0 is the initial value passed to .reduce() as the second argument. Return sum od 0 and 1, which is 1.
  • Call function on previous result ( which is 1 ) and next array element. This returns sum of 1 and 2, which is 3
  • Repeat until last element, which will sum up to 21

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10-15 16:03