Use slice to encapsulate array methods in JS

This article introduces to you about using slice to encapsulate array methods in JS. It has certain reference value. Friends in need can refer to it.

Function of slice method
// 1) : Array interception
// 2) :slice(m,n): Starting from array index m, intercept to index n, but not included n;[Include before and not after]
// slice(m): Starting from index m, intercept to the end;
// slice(): clone slice(0) of the array;
// // Negative index: Make the current length negative;
// 3): The return value is the intercepted array
// 4): The original array does not change;
/**
* First of all: first distinguish several situations of slice and the idea of ​​slice
* The parameters passed can be other types of data, as long as they can be converted into valid numbers (so the parameter type requirements are more flexible)
* Secondly, it should be noted that only the first and second parameters are valid parameters, the third and subsequent parameters will have no impact on the intercepted result

Processing of parameters:
* Let’s temporarily give the first parameter to the variable start, and the second parameter to the variable end
* 1. When parameter 1 and parameter 2 are both undefined or one of them is undefined Case
* Case 1: When parameter 1 is undefined, directly take start=0
* Case 2: When parameter 2 is undefined, directly take end=this.length

2. When neither parameter 1 nor parameter 2 is undefined
* Case 1: When the first parameter is a negative number: start takes the maximum value of this.length and the parameters; when the first When the parameter is greater than or equal to 0, start directly takes itself
* Case 2: When the second parameter is a negative number, end takes the sum of this.length and end; when the parameter is greater than 0, end takes this.length With the minimum value in end

Processing of interval length: Set size=end-start
* Case 1: When the interval length is less than or equal to 0, return empty directly Array
* Case 2: When the interval length is greater than 0, whether for a string or an array, create an array with a length of size, assign values ​​to the new array from start to end, and return the new array
@type {Array}
*/
Attached code:

    Array.prototype.mySlice = function (start,end) {
        var newAry = [];//创建一个变量用来接收返回值
        var len = this.length;//变量接收当前数组的长度
        //先对参数为undefined的情况进行处理
        start = (start !== undefined)?start:0;
        end = (end !== undefined)?end:len;
        //对于参数的处理，采用三目运算符,由于在与0判断的时候自动转换为数字再进行判断，所以直接与0比较即可
        start = (start>=0)?start:Math.max(0,len+start);
        end = (end>=0)?Math.min(end,len):len+end;
        var size = end - start;//用一个变量接收截取区间的长度
        if(size>0){
            //当区间长度大于0时，实例化一个长度为size的数组，并赋值给newAry
            newAry = new Array(size);
            //遍历数组，将当前数组[start,end)区间上的值依次赋值给newAry
            for(var i = 0;i<size;i++){
                newAry[i] = this[i+start];
            }
        }else{
            //当区间长度小于等于0的情况下，直接返回空数组
            return newAry;
        }
        return newAry;
    };

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