我无法理解这段代码

Question

我不得不删除数组中的相同数据。
我发现这段代码及其工作方式完全符合我的要求，但我无法理解这段代码的一部分。
请解释这段代码和这是什么 >>> a[this[i]] <<<

Array.prototype.unique = function() {
    var a = {}; //new Object
    for (var i = 0; i < this.length; i++) {
        if (typeof a[this[i]] == 'undefined') {
            a[this[i]] = 1;
        }
    }
    this.length = 0; //clear the array
    for (var i in a) {
        this[this.length] = i;
    }
    return this;
  };

Answer 1

a[this[i]] =>
this[i] -> 从当前对象中获取 i 元素，在本例中为 Array.
a[] -> 在 [] 中指定的位置从 var a 获取元素，在这种情况下，this[i]

中的值是什么

Answer 2

请查看解释该行代码的每一行之前的注释 //向数组原型添加唯一函数，以便所有数组都可以具有唯一 //函数访问

    Array.prototype.unique = function() {
        //creating a temp object which will hold array values as keys and 
         //value as "1"  to mark that key exists
        var a = {}; //new Object
        //this points to the array on which you have called unique function so
        //if arr = [1,2,3,4] and you call arr.unique() "this" will point to 
        //arr in below code iterating over each item in array
        for (var i = 0; i < this.length; i++) {
        //idea is to take the value from array and add that as key in a so 
        //that next time it is defined. this[i] points to the array item at 
        //that index(value of i) //and a[this[i]] is adding a property on a 
        //with name "this[i]" which is the value //at that index  so if value 
        //at that index is lets say 2 then a[this[i]] is //referring to 
        //a["2"].thus if 2 exists again at next index you do not add it to a
        //again as it is defined
            if (typeof a[this[i]] == 'undefined') {
                a[this[i]] = 1;
            }
        }
        this.length = 0; //clear the array
        //now in a the properties are unique array items you are just looping 
        //over those props and adding it into current array(this) in which 
        //length will increase every //time you put a value 
        for (var i in a) {
            this[this.length] = i;
        }
        //at the end returning this which is the modified array
        return this;
      };

//编辑

a[this[i]] 的存储值是 1，对于 a 中的所有键，它将是一个。你从

开始

arr = [1,2,3,2,3,4];

当你打电话给 arr.unique 第一个循环中的代码创建了一个类似这样的东西

a = {
"1":1,
"2":1,
"3":1,
"4":1
}

因此您可以看到只有唯一值作为 a 中的属性。现在在 for-in 循环中，您只是获取 a(ie 1,2,3,4) 的键并将其添加到数组 (this).

如果您需要更多详细信息，希望这有助于让我知道

我无法理解这段代码

I can not understand this code

javascript

arrays

typeof