Javascript Scope Issue

Question

I'm trying to get this function to work. I think the function is pretty self explanitory:

function FileExists(path){
    var result = false;

    $.ajax({
        url:    "http://mydomain.com/"+path,
        type:   "HEAD",
        success:
                function(){
                    result = true;
                }
    });

    return result;
}

I need the anonymous function that is called upon success of the ajax post to set the variable "result" that was defined inside the FileExists function to true so that I can return that value from the FileExists function. I think I need a closure for this but they confuse the hell out of me.

Please help! Thanks!

Answer 1

It's not a scoping issue, but rather because $.ajax is asynchronous, meaning that FileExists will return before $.ajax will complete. What you should be doing is to move all code that depends on result to inside the success callback.

Answer 2

Ajax calls are by default asynchronous, you can either use a callback function:

$.ajax({
    url:    "http://mydomain.com/"+path,
    type:   "HEAD",
    success: function(){
        callback(true);
    }
});

Or make the call synchronously.

$.ajax({
    async:   false,
    url:    "http://mydomain.com/"+path,
...