// 模拟实现call方法

Function.prototype.call2 = function (context) {

    var context = context || window;

    context.fn = this;

    var args = [];

    for(var i = 1, len = arguments.length; i < len; i++) {

        args.push('arguments[' + i + ']');

    }

    var result = eval('context.fn(' + args +')');

    delete context.fn

    return result;

}

// 测试一下

var value = 2;

var obj = {

    value: 1

}

function bar(name, age) {

    console.log(this.value);

    return {

        value: this.value,

        name: name,

        age: age

    }

}

bar.call(null); // 2

console.log(bar.call2(obj, 'kevin', 18));

// 模拟实现apply方法

Function.prototype.apply = function (context, arr) {

    var context = Object(context) || window;

    context.fn = this;

    var result;

    if (!arr) {

        result = context.fn();

    }

    else {

        var args = [];

        for (var i = 0, len = arr.length; i < len; i++) {

            args.push('arr[' + i + ']');

        }

        result = eval('context.fn(' + args + ')')

    }

    delete context.fn

    return result;

}

// 模拟实现Bind方法

Function.prototype.bind = function (oThis) {

  var aArgs = Array.prototype.slice.call(arguments, 1)；

  var fToBind = this；

  var fNOP = function () {}；

  var fBound = function () {

    fBound.prototype = this instanceof fNOP ? new fNOP() : fBound.prototype；

    return fToBind.apply(this instanceof fNOP ? this : oThis || this, aArgs )

  }

  if( this.prototype ) {

    fNOP.prototype = this.prototype；

  }

  return fBound；

}