SetTimeout and recursivity with cucumber

Question

I have a function written in javascript calling itself in a recursive way :

function f(attempt){
    if (attempt + 1 <= 10) {
        setTimeout(f(attempt + 1),2000);
    }
}
f(0);

For an unknown reason the function is effectively called 10 times but without any delay. The setTimeout seems to execute immediately the function f.

However when I do this then everything works fine :

function f(attempt){
if (attempt + 1 < 10) {
    setTimeout(function(){f(attempt + 1);},2000);
}}
f(0);

Do you have an explanation ? Is is because this code is written for Cucumber testing ?

Answer 1

You have to pass the function as a parameter to setTimeout, that means no parenthesis at the end of f. What you are doing right now is calling f and passing it's return value to setTimeout. You can pass arguments to f as the third argument of setTimeout. Your call should look like this:

setTimeout(f, 2000, attempt + 1);

Answer 2

setTimeout(f(attempt + 1),2000);

This code above calls setTimeout function and instead of passing a function to call it passes the result of your f() function, it is invoked right on the spot.

  setTimeout(function() { f(attempt + 1) },2000);

But in this case you are passing a reference to your function to be invoked in a 2000 seconds, so it does not evaluate the function itself on the spot.

Answer 3

You should write it like this. This is an alternative way to do the check and have no private vars.

function f(){
 if(++attempt<10){// not shure 
  setTimeout(f,2000);
 }
}
var attempt=0;
f();

Demo

http://jsfiddle.net/3nm2Q/