JS模拟实现callapplybind

Posted 2021-02-18 ckang

function call_mock (obj) {
    var aim_fun = this;
    var argument = [];
    for (var i = 1; i < arguments.length; i++) {
        argument.push(arguments[i]);
    }
    obj.aim_fun = aim_fun;
    var result = eval(‘obj.aim_fun(‘+ argument.join() + ‘)‘);
    delete obj.aim_fun;
    return result;
}

Function.prototype.call_mock = call_mock;

function apply_mock (obj, args) {
    var aim_fun = this;
    obj.aim_fun = aim_fun;
    var result = eval(‘obj.aim_fun(‘+ args.join() + ‘)‘);
    delete obj.aim_fun;
    return result;
}

Function.prototype.apply_mock = apply_mock;

function bind_mock (obj) {
    var aim_fun = this;
    var argument = [];
    for (var i = 1; i < arguments.length; i++) {
        argument.push(arguments[i]);
    }
    var fNOP = function () {};
    var fBound = function () {
        return aim_fun.apply_mock(obj, argument)
    }
    fNOP.prototype = this.prototype;
    fBound.prototype = new fNOP();
    return fBound;
}

Function.prototype.bind_mock = bind_mock;

var a = {
    c:1,
    see(a, b) {
        console.log(`${this.c}${a}${b}`);
    }
}

c = 0;

a.see.bind_mock(global, 1, 2);

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Function.prototype.mycall = function(context) {
    var context = context || window;
    // 给context添加一个属性
    context.fn = this;
    // 获取参数
    var args = [...arguments].slice(1);
    // 执行该函数
    var result = context.fn(...args);
    // 删除fn    
    delete context.fn;
    // 返回执行结果
    return result;
}

Function.prototype.myapply = function(context) {
    var context = context || window;

    context.fn = this;

    var result = null;

    if(arguments[1]) {
    
        result = context.fn(...arguments);
        
    }else {
    
        result = context.fn();
        
    }
    
    delete context.fn;

    return result;
}

Function.prototype.mybind = function(context) {
    if(typeof this !== ‘function‘) {
    
        throw new TypeError(‘Error‘);
        
    }
    
    var _this = this;

    var args = [...arguments].slice(1);

    return function F() {
    
        if(this instanceof F) {
        
            return new _this(...args, ...arguments);
            
        }
        
        return _this.apply(context, args.concat(...arguments));
        
    }
}