javascript中奇怪的关联数组行为

Question

If I execute below code on chrome console then, I got answer as associative array: 如果我在chrome控制台上执行下面的代码然后，我得到了作为关联数组的答案：

var arr= [];
var i = 1;
for(var j = 1; j < 3; j++)
    arr[j]=j;console.log(arr);

Ans : [1: 1, 2: 2] 答案： [1: 1, 2: 2]

But when i execute using node: [ , 1, 2 ] 但是当我使用node执行时： [ , 1, 2 ]

Why there is so difference? 为什么会有这么大的差异？ As far as i know both are using v8. 据我所知，两人都在使用v8。

Answer 1

Firefox says Firefox说

Array [ <1 empty slot>, 1, 2 ]

IE Edge says IE Edge说

[object Array][undefined, 1, 2]

and, they're all correct 而且，他们都是正确的

Chrome is simply NOT reporting the empty index 0 Chrome只是不报告空索引0

Node is showing index 0 is empty 节点显示索引0为空

Firefox is telling you exactly what's happening Firefox正在告诉你到底发生了什么

Try this: 试试这个：

var arr= [];var i = 1; for(var j = 1; j < 3; j++) arr[j*3]=j+3;console.log(arr);

Firefox: 火狐：

Array [ <3 empty slots>, 4, <2 empty slots>, 5 ]

Node 节点

[ , , , 4, , , 5 ]

IE Edge IE Edge

[object Array][undefined, undefined, undefined, 4, undefined, undefined, 5]

Chrome 铬

[3: 4, 6: 5]