JS Memory Leak Tools & Tips

Javascript Closure

If you refresh the browser or go to another page and the memory doesn’t go down you probably have a closure. I just ran into a tricky situation where my closure was being caused during the successful call back of a JQuery Ajax call.

The function that was leaking looked like this:

function <span>GetData</span>(object) {

var requestObject = object.buildRequest()

$.ajax({
type: "POST",
url: object.url,
dataType: "json",
data: requestObject,
success: function(jsonResult) {
object.data = jsonResult;
object.DoStuffWithData();
}
});
}

The fix was to remove the object from being a local variable.

function GetData(object) {

var requestObject = object.buildRequest()

$.ajax({
type: “POST”,
url: object.url,
dataType: “json”,
data: requestObject,
success: function(data) {
//On Success Call Data Updater
data.id = object.Id;
DataUpdater(data);
}
});

requestObject = null;
}

function DataUpdater(data) {

//loop through Requesters Array

//must add object to global array before making DataUpdater
for (i = 0; i < Requesters.length; i++) { var temp = Requesters[i]; var requestId = temp.Id; var dataId = data.Id; //Find object with matching id if (requestId == dataId ) { temp .data = data; temp .DoStuffWithData(); } } } [/js] Drip
While tracking down this memory leak I decided to try out a memory leak tool called Drip. Unfortunately, It didn’t work in my situation. Drip actually started causing memory leaks so it made it hard to tell if I actually fixed the problem or not. I think the reason it doesn’t work is the script is recursive using setInterval.