For in loop not working with global namespace variable

Question

I'm working on a canvas animation/game and I am having problems with a for in loop in one of my functions. In the interest space I removed some code.

function LoadScene(){ // function with the issue
                console.dir(game.frames); //195 objects 0{}, 1{}, 2{}, etc.
                for (var prop in game.frames){
                    console.log(prop); //Does not get here
                    if (game.frames[prop].scene == game.currentScene){
                        game.sceneData.push(game.frames[prop]);
                    }
                }
            }

function LoadFrames(){
                //xhr request
                // if successs load json data into namespace variable
                // get canvas
                // drawImage Loading Screen
                // return true

}


function StartGame(){
   if(LoadFrames()){
       LoadScene();
   }
}

The for in loop just fails every time (never goes into the loop) even though there are items in the in the object. I thought it might have been a hoisting issue so I put all my variables into a namespace at the top of the script and rearranged my functions. I think it could also be a async issue since the function works when I use the debugger to step through the function, but if that is the case then I have no idea how to fix it.

`just fails` in what way? error in the console? never enters the loop? castrates your dog? — Jaromanda X, Sep 02 '16 at 02:21
*"I think it could also be a async issue"* - I think this is it. Can you call `LoadScene()` from within `LoadFrames()` Ajax code, or use a promise or callback mechanism to wait for the load to finish? — nnnnnn, Sep 02 '16 at 02:21
You need to call `LoadScene()` from the `xhr.onreadystatechange` function. — Barmar, Sep 02 '16 at 02:32
@JaromandaX It never goes into the loop, not unless I step into it using the debugger. — user3314802, Sep 02 '16 at 09:37
then the duplicate question will give you all you need to know — Jaromanda X, Sep 02 '16 at 09:38

score 0 · Answer 1 · answered Sep 02 '16 at 02:32

function LoadFrames(){
            //xhr request
            // if successs load json data into namespace variable
            // get canvas
            // drawImage Loading Screen
            // return true
}

The XMLHttpRequest within LoadFrames may work asynchronously, whereas LoadFrames works synchronously. LoadFrames always returns true immediately after sending the AJAX request, regardless of if the frames(maybe you mean game.frames?) have been loaded; i.e. it does not check the response of the request.

For in loop not working with global namespace variable

1 Answers1