How synchronous AJAX call could cause memory leak?

Question

I understand this general advice given against the use of synchronous ajax calls, because the synchronous calls block the UI rendering.

The other reason generally given

Answer 1

Memory leaks using syncronous AJAX requests are often caused by:

• using setInterval/setTimout causing circular calls.
• XmlHttpRequest - when the reference is removed, so xhr becomes inaccessible

Memory leak happens when the browser for some reason doesn’t release memory from objects which are not needed any more.

This may happen because of browser bugs, browser extensions problems and, much more rarely, our mistakes in the code architecture.

Here's an example of a memory leak being cause when running setInterval in a new context:

var
Context  = process.binding('evals').Context,
Script   = process.binding('evals').Script,
total    = 5000,
result   = null;

process.nextTick(function memory() {
  var mem = process.memoryUsage();
  console.log('rss:', Math.round(((mem.rss/1024)/1024)) + "MB");
  setTimeout(memory, 100);
});

console.log("STARTING");
process.nextTick(function run() {
  var context = new Context();

  context.setInterval = setInterval;

  Script.runInContext('setInterval(function() {}, 0);',
                      context, 'test.js');
  total--;
  if (total) {
    process.nextTick(run);
  } else {
    console.log("COMPLETE");
  }
});