apply模拟实现疑问

[WuliWalter]

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;
}

前辈，apply模拟实现arr不能直接用吗为什么还要

 var args = [];
        for (var i = 0, len = arr.length; i < len; i++) {
            args.push('arr[' + i + ']');
        }
        result = eval('context.fn(' + args + ')')

做一次这样的操作

[mqyqingfeng]

@WuliWalter 可以参考这个回答 https://github.com/mqyqingfeng/Blog/issues/11#issuecomment-302026366_