How to destroy a JavaScript object?

Question

Recently, I came across one of my application which consumes too much memory and increasing by 10 MB/sec.

So, I like to know the best way to destroy JavaScript object and variables so memory consumption stay down and my FF can't get destroyed.

I am calling two of my JavaScript in every 8 sec interval without reloading the page.

function refresh() {
    $('#table_info').remove();
    $('#table').hide();
    if (refreshTimer) {
        clearTimeout(refreshTimer);
        refreshTimer = null ;
    }
    document.getElementById('refresh_topology').disabled=true; 
    $('<div id="preload_xml"></div>').html('<img src="pic/dataload.gif" alt="loading data" /><h3>Loading Data...</h3>').prependTo($("#td_123"));
    $("#topo").hide();
    $('#root').remove();
    show_topology();
}

How can I see which variable cause Memory overhead and method to stop execution of that process?

Answer 1

You could put all of your code under one namespace like this:

var namespace = {};

namespace.someClassObj = {};

delete namespace.someClassObj;

Using the delete keyword will delete the reference to the property, but on the low level the JavaScript garbage collector (GC) will get more information about which objects to be reclaimed.

You could also use Chrome Developer Tools to get a memory profile of your app, and which objects in your app are needing to be scaled down.

Answer 2

You can't delete objects, they are removed when there are no more references to them. You can delete references with delete.

However, if you have created circular references in your objects you may have to de-couple some things.

Answer 3

While the existing answers have given solutions to solve the issue and the second half of the question, they do not provide an answer to the self discovery aspect of the first half of the question that is in bold: "How can I see which variable cause Memory overhead...?"

It may not have been as robust 3 years ago, but the Chrome Devevloper Tools "Profiles" section is now quite powerful and feature rich. The Chrome team has an insightful article on using it and thus also how garbage collection (GC) works in javascript, which is at the core of this question.

Since delete is basically the root of the currently accepted answer by Yochai Akoka, it's important to remember what delete does. It's irrelevant if not combined with the concepts of how GC works in the next two answers: if there's an existing reference to an object it's not cleaned up. The answers are more correct, but probably not as appreciated because they require more thought than just writing 'delete'. Yes, one possible solution may be to use delete, but it won't matter if there's another reference to the memory leak.

delicateLatticeworkFever appropriately mentions circular references and the Chrome team documentation can provide much more clarity as well as the tools to verify the cause.

Since delete was mentioned here, it also may be useful to provide the resource Understanding Delete. Although it does NOT get into any of the actual solution which is really related to js's GC.

Answer 4

Structure your code so that all your temporary objects are located inside closures instead of global namespace / global object properties and go out of scope when you've done with them. GC will take care of the rest.

Answer 5

I was facing a problem like this, and had the idea of simply changing the innerHTML of the problematic object's children.

adiv.innerHTML = "<div...> the original html that js uses </div>";

Seems dirty, but it saved my life, as it works!