等价于ES5的bind()

es5_bind.js

if (!Function.prototype.bind) {
    Function.prototype.bind = function (obj) {
        var slice = [].slice,
            args = slice.call(arguments, 1),
            self = this,
            nop = function () {},
            bound = function () {
                return self.apply( this instanceof nop ? this: (obj || {}), args.concat(slice.call(arguments)));
            };

        nop.prototype = self.prototype;

        bound.prototype = new nop();

        return bound;
    }
}

// from JavaScript Web Applications by MacCaw