javascript - 为什么JavaScript数组的最大索引是4294967294而不是4294967295？

Question

这个问题已经有答案了:

Why is a JavaScript Array index at most 4294967294 but not 4294967295? (3 个回答)

已关闭 6 年前。

我正在学习 JavaScript，最近遇到了一个关于 JavaScript 数组的问题。

JavaScript的数组的数字索引被描述为32位，我认为它的最大索引是2的32次方减1，但右边是2的32次方减2。我不知道为什么？谁能告诉我吗？

Answer 1

发布此内容是为了表明您关于最大 INDEX 为 4294967294 的说法是正确的，因为它的最大长度为 -1，而最大长度为 2³²-1

所以从 0 到 4294967294 你有 4294967295 个元素

所有 JS 数组都从 0 开始

new Array(4294967295) 是您可以定义的最大数组，因为您需要将 unsigned int 传递给构造函数因此您可以拥有的最大索引比该值小 1

MDN Array

arrayLength

If the only argument passed to the Array constructor is an integer between 0 and 2³²-1 (inclusive), this returns a new JavaScript array with its length property set to that number (Note: this implies an array of arrayLength empty slots, not slots with actual undefined values). If the argument is any other number, a RangeError exception is thrown.

<小时/>

Wikipedia
The number 4,294,967,295, equivalent to the hexadecimal value FFFFFFFF, is the maximum value for a 32-bit unsigned integer in computing. It is therefore the maximum value for a variable declared as an unsigned integer

var arr = new Array(4294967294);
arr[arr.length-1]="one but last";
console.log("Length: "+arr.length,"Index = "+(arr.length-1)+": "+arr[arr.length-1]); 
arr.push("Last");
console.log("Length: "+arr.length,"Index = "+(arr.length-1)+": "+arr[arr.length-1]); 
arr.push("One too far");
console.log("Length: "+arr.length,"Index = "+(arr.length-1)+": "+arr[arr.length-1]);