Question

This is my code:

var b;
while(!b){
    setTimeout(function(){
        alert('sss')
        b=1;
    }, 500);
}

and it will not alert ‘sss’

What can i do?

Updated:

I want to get bounds on google maps v3:

function get_bounds(){
            var bounds_;
            while(!bounds_){
                setTimeout(function(){
                    bounds_=map.getBounds();
                    if(bounds_){
                        var leftBottom=[bounds_.getSouthWest().lat(),bounds_.getSouthWest().lng()]
                        var rightTop=[bounds_.getNorthEast().lat(),bounds_.getNorthEast().lng()]
                        return [leftBottom,rightTop];
                        }
                }, 500);
            }
        }

updated2:

hi patrick dw, i don’t know why , but your code doesn’t work:

var b;
function waitForB() {
    setTimeout(function(){
        if(!b)
            waitForB();
        else
            alert('sss');
    }, 500);
}
waitForB()

updated3:

it is ok now :

var b;
function waitForB() {
    setTimeout(function(){
        if(!b){
            waitForB();
            b='ss';
        }
        else{
            alert('sss')
        }
    }, 500);
}
waitForB()

Answer 1

JavaScript in web browsers is run in a single thread. When you call setTimeout(), it won’t spawn a new thread. This means that setTimeout() will not execute until all of your main code has finished executing.

For this reason, you will end up with an infinite loop, because your loop condition is dependant on the execution of the setTimeout() callback.

Here’s an interesting article on how JavaScript timers work:

• How JavaScript Timers Work by John Resig

---

UPDATE:

Further to the updated question, you may want to listen to the bounds_changed event instead. I am not sure how you are planning to use your get_bounds() function, but you may want to refactor your logic to use an event listener instead:

google.maps.event.addListener(map,'bounds_changed', function () {
   // The code here is triggered when the bounds change
});