js中Array方法重寫（一）：myPush()，myPop()，myUnshift()，myShift()

1、myPush()

//myPush() 數組入棧
Array.prototype.myPush = function(){
    var L = this.length;
    for(var i = L ; i < L + arguments.length ; i++){
        this[i] = arguments[i - L];
    }
    return this.length;
}

2、myPop()

//Mypop() 數組出棧
Array.prototype.myPop = function(){
    if (this.length == 0) {
        return undefined;
    }
    var last = this[this.length-1];
    this.length = this.length-1;
    return last;
}

3、myUnshitf()

//myUnshift 數組入隊
Array.prototype.myUnshift = function(){
    var L = this.length;
    for(var i = L + arguments.length - 1 ; i >= 0 ; i--){
        if(i > arguments.length - 1){
            this[i] = this[i - arguments.length];
        }else{
            this[i] = arguments[i];
        }
    }
    return this.length;
}

4、myShitf()

//myShift()數組出隊
Array.prototype.myShift = function(){
    if (this.length == 0) {
        return undefined;
    }
    var firstElement = this[0];
    for(var i = 1 ; i < this.length ; i++){
        this[i-1] = this[i];
    }
    this.length = this.length-1;
    return firstElement;
}

純手寫，若有不善，請指正 ^_^