试图为函数和passvariable设置timeout - 不起作用

Question

Basically I have a function that passes this... I need this function to be executed 1/3 seconds after a button got clicked so what I thought of doing is:

setTimeout("somefunction(this)", 3000);

As I know that setTimeout("", x); works with "" but it doesn't work.

I've tried without the "" and it wont work either I tried to:

  setTimeout("somefunction("+this+")", 3000);

and still won't work. Did like an hour of attempts at this.

Any help would be highly appreciated.

Answer 1

You need to use a closure

var that = this;
setTimeout( function(){ somefunction(that); }, 3000);

Answer 2

timeouts are asynchronous events and so the context is lost. One way to preserve it is to bind it via an immediately-executed function.

setTimeout((function(that) {
    return function() { somefunction(that); };
})(this), 3000);

Another way would be to make a reference to the outer scope in a variable, as @epascarello's answer shows.

It is always better to pass function references to setTimeout and setInterval than strings, because the latter are evaluated, and eval'ing is evil.