通过原型链实现数组内置方法[JavaScript_013]

push()实现

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Array.prototype.push = function() {
    for (var i = 0; i < arguments.length; i++) {
        this[this.length] = arguments[i];
    }
}

unshift()实现

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Array.prototype.unshift = function() {
    var output = [];
    for (var i = 0; i < arguments.length; i++) {
        output[output.length] = arguments[i];
    };
    for (var i = 0; i < this.length; i++) {
        output[output.length] = this[i];
    };
    for (var i = 0; i < output.length; i++) {
        this[i] = output[i];
    };
    return this.length;
}

reverse()实现

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Array.prototype.reverse = function() {
    var output = [];
    for (var i = this.length - 1; i >= 0; i--) {
        output.push(this[i]);
    }
    for (var i = 0; i < output.length; i++) {
        this[i] = output[i];
    };
    return this.length;
}

sort()自定义排序方法

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• 规则：
  1. 自定义的排序方法，必须传入两个形参
  2. 返回的值为负数时，前面的数字在前，反之，后面的在前
  3. 返回0时不变化
     return a-b 为升序排序，b-a为降序排序