Question

There is an error in the following code:

generate: function() {
    var generated = [];
    for (var j = 0; j < objectDefinitions.length; j++) {
        var randomNumber;

        if (!objectDefinitions[j].restrictGeneration) {
            continue;
        }

        randomNumber = Math.random();

        if (randomNumber < objectDefinitions[j].probability) {
            generated.push(objectDefinitions[j].createObject());
            objectDefinitions[j].restrictGeneration = true;
            if (j > 5) {
            }
            setTimeout(function() {                 
                //console.log(j);
                objectDefinitions[j].restrictGeneration = false;
            }, objectDefinitions[j].cooldown);
        }
    }
    return generated;
}

When the setTimeout “fires” the variable j is 6, which causes an array index out of bounds exception because there are only 6 items in the array. I don’t really understand what’s going on, I have checked j outside setTimeout and it is never 6, but it seems to change after it’s declaration. Thanks for any help.

Answer 1

The variables j it reads is the one you used in the loop so it didn’t get “copied”.

setTimeout(
    (function(k){
        return function() {            
            objectDefinitions[k].restrictGeneration = false;
        };
    }(j))
, objectDefinitions[j].cooldown);

This way you j is copied in a k variable. But there is one k variable per iteration of the loop.