手写bind
修改 this 指向
http://www.nowcoder.com/questionTerminal/a616b3de81b948fda9a92db7e86bd171
function bindThis(f, oTarget) {
let args = Array.prototype.slice.call(arguments, 2);
return function(){
return f.apply(oTarget, Array.prototype.slice.call(arguments).concat(args));
}
}
