bind手写(Lucas小册1-1番外篇)

普通版本

Function.prototype.bind = Function.prototype.bind || function (context) {
        var me = this;
        //伪数组转换成数组,并且预存初始参数
        var args = Array.prototype.slice.call(arguments, 1);
        console.log(me)
        console.log(args)
        return function bound () {
            //获取二次传入的参数
            var innerArgs = Array.prototype.slice.call(arguments);
            //拼为最终参数
            var finalArgs = args.concat(innerArgs);
            console.log(innerArgs)
            console.log(finalArgs)
            return me.apply(context, finalArgs);
        }
    }

能在构造函数场景下兼容

Function.prototype.bind = Function.prototype.bind || function (context) {
    if (typeof this !== "function") {
        throw new TypeError("Function.prototype.bind - what is trying to be bound is not callable");
      }
    var me = this;
    var args = Array.prototype.slice.call(arguments, 1);
    var F = function () {};
    F.prototype = this.prototype;
    var bound = function () {
        var innerArgs = Array.prototype.slice.call(arguments);
        var finalArgs = args.concat(innerArgs);
        return me.apply(this instanceof F ? this : context || this, finalArgs);
    }
    bound.prototype = new F();
    return bound;
}

bind的偏函数用法,可以用于预设参数

function list(){
    return Array.prototype.slice.call(arguments)
}

function addAuguments(arg1,arg2){
    return arg1+arg2
}

let listRe = list.bind(null,37)
let addRe = addAuguments.bind(null,37)

console.log(listRe(12,54))//[ 37, 12, 54 ]
console.log(addRe(12,54))//49