This article introduces you to the article about JS encapsulated array prototype: an introduction to the use of the sort method. It has a good reference value. I hope it can help friends in need.

Based on native JS encapsulation of the sort method on the array prototype

I recently learned about the encapsulation of built-in methods on the array prototype, which strengthened my ability to encapsulate methods with native JS and further understood The process of encapsulating array methods and the functions implemented. Although I didn't go deep into the bottom layer and understand the source code. The following solutions are all based on personal understanding of functions implemented using pure native JS. If there is something wrong, you can tell me in the comments

First, let’s take a look at the function, parameters, and return value of the method. Whether the original array is Changes

The sort method is mainly used for sorting arrays
The parameters are divided into two types:

One: pass The parameter is a function (the sorting mainly depends on the return value of the function)

Another method: passing is not a function, or does not pass it (as long as it is not a function, the original sorting process will not be affected) Impact)
The return value of the method is the sorted array of the original array
The original array has changed, it is the sorted array

Secondly, let’s take a look at the comparison between the various situations to be handled by the sort method

Case 1: No parameter implementation for string array Sorting
Case 2: No-parameter implementation for sorting arrays of type number
Case 3: No-parameter implementation for sorting arrays of mixed types such as strings and numbers Sorting
Case 4: With parameters, implement sorting of numerical data of type number
Case 5: With parameters, sort() sorts the custom attributes of simple object List
Case 6: With parameters, you can sort arrays of mixed types of strings and numbers.

The processing of parameters by the sort method:

Case 1: If the parameter is not a function, the original sorting process will not be affected
Case 2: If the parameter is a function, sorting will be performed based on the return value in the callback function. If the return value is greater than 0, the positions are swapped; if the return value is less than 0, the positions are not swapped
If the return value is not a number, the positions are not swapped

Based on Based on the discussion of the above situation, the core principle of sort method implementation is as follows:

Core principle: without parameters (and with parameters that are not functions): default ascending order
Without parameters, convert the string directly and compare the ASCII code values one by one
No exchange as long as one of them is an object {}
With parameters as a function:
According to the function The return values are compared; if the function return value is greater than 0; the positions are swapped

`The implementation code is as follows:`

Array.prototype.mySort = function(fn){
    if(Object.prototype.toString.call(fn)===&#39;[object Function]&#39;){
        //如果传进来参数的是函数
        for(var i = 0;i<this.length-1;i++){
            //遍历数组,将前后两项作为实参传给fn
            if(fn.call(this,this[i],this[i+1])>0){
                //如果fn执行之后的返回值大于0.就调用swap方法交换位置
                var a = this[i],b=this[i+1];
                this[i] = swap(a,b).a;
                this[i+1] = swap(a,b).b;
                //交换之后，如果当前项不是第一项，则当前项(索引为i的项)继续跟前面的项进行比较
                if(i>0){
                    for(var j = i-1;j>=0;j--){
                            if(fn.call(this,this[j],this[j+1])>0){
                                var a = this[j],b=this[j+1];
                                this[j] = swap(a,b).a;
                                this[j+1] = swap(a,b).b;
                            }
                        }
                }
            }
        }
    }else{
        //如果不是函数，则按正常排序
        //遍历数组，将前后两项进行比较
        for(var i = 0;i<this.length-1;i++){
            var cur = this[i];//当前项
            var next = this[i+1];//下一项
            if(comASCII(cur,next)){
                //当返回true的时候交换，并且交换完成之后，当前项继续往前比较
                this[i] = swap(cur,next).a;
                this[i+1] = swap(cur,next).b;
                //当前项继续向前比较
                if(i>0){
                    for(var k = i-1;k>=0;k--){
                        var cur = this[k];
                        var next = this[k+1];
                        if(comASCII(cur,next)){
                            this[k] = swap(cur,next).a;
                            this[k+1] = swap(cur,next).b;
                        }
                    }
                }
            }
        }
    }
    //封装一个交换位置的函数
    function swap(a,b){
        return {
            a:b,
            b:a
        }
    }
    //如果不传参的情况下比较ASCII码
    function comASCII(cur,next){
        //全部转换为字符串、逐项比较ASCII码
        cur = cur.toString();
        next = next.toString();
        //取长度最大值
        var len = cur.length>next.length?next.length:cur.length;
        //当前后两项都不是不是{}类型的数据时，进行比较
        if(cur!==&#39;[object Object]&#39;&&next!==&#39;[object Object]&#39;){
            for(var j = 0;j<len;j++){
                if(!isNaN(cur.charCodeAt(j))&&!isNaN(next.charCodeAt(j))){
                    //如果二者的ASCII码都是有效数字
                    if(cur.charCodeAt(j)>next.charCodeAt(j)){
                        //如果前一项比后一项当前的ASCII码大，则返回true，交换位置
                        return true;
                    }else if(cur.charCodeAt(j)==next.charCodeAt(j)){
                    //如果相等直接进入下一轮循环
                            continue;
                        }else{
                        //前项比后项小，直接返回false
                            return false;
                        }
                }
            }
            if(!isNaN(cur.charCodeAt(len))&&isNaN(next.charCodeAt(len))&&(cur.charCodeAt(len-1)==next.charCodeAt(len-1))){
                //比较完之后，如果前一项ASCII还是有效数字，说明前项比后项大，交换
                return true;
            }
        }
        //如果上述条件不满足，则不交换
        return false;
    }
    //返回当前数组
    return this;
};

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