问题描述

有人可以解释以下两个输出吗?

Can someone explain the following two outputs?

代码 1:

console.log(itemsAry);
//loadNextItem();
function loadNextItem(){
    var item = itemsAry.shift();
    console.log(item);
}

结果:

["cat-53", "cat-57", "cat-51", "cat-10", "cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]

(如预期).

代码 2:

console.log(itemsAry);
loadNextItem();
function loadNextItem(){
    var item = itemsAry.shift();
    console.log(item);
}

结果:

["cat-57", "cat-51", "cat-10", "cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]

cat-53

请注意，cat-53 已从原始数组 PRIOR 转移到 console.log() 输出，该输出应该在 shift 操作之前发生地方.我怎么可能?或者我错过了什么?

Notice that cat-53 has been shifted from the original array PRIOR to the console.log() output that is supposed to be occurring BEFORE the shift operation ever takes place. How i this possible? Or what am I missing?

情况变得更糟:

console.log(itemsAry);
loadNextItem(); loadNextItem(); loadNextItem(); loadNextItem();
function loadNextItem(){
    var item = itemsAry.shift();
    console.log(item);
    console.log(itemsAry);
}

结果:

["cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-53
["cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-57
["cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-51
["cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-10

在 FireFox 中进行测试后，这似乎是特定于 Google Chrome 的问题.FF 输出:

After testing in FireFox, it appears to be a Google Chrome issue specifically. FF output:

["cat-53", "cat-57", "cat-51", "cat-10", "cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-53
["cat-57", "cat-51", "cat-10", "cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-57
["cat-51", "cat-10", "cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-51
["cat-10", "cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]
cat-10
["cat-55", "cat-56", "cat-5", "cat-50", "cat-3", "cat-54", "cat-52", "cat-9", "cat-8", "cat-4", "cat-58", "cat-6", "cat-7"]

按预期输出...

推荐答案

console.log 总是有点迟到"，当涉及到对象时，你不能指望它.只有原语(字符串等)才能直接工作.前者在内存中只有一个实例，所以当控制台获取数据时，它可能已经改变了.

console.log is always a little "late" and you can't count on it when it comes to objects. Only primitives (strings etc.) will work directly. Of the former there is only one instance in memory, so when the console is fetching the data it may have changed already.

当然，这取决于您实际使用的控制台，但我经常在 Chrome 上遇到这种情况.

Of course, it depends on which console you're actually using, but I'm frequently experiencing this on Chrome.

这里有人在萤火虫.

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