There are many ways to create a memory leak in Javascript. Here is a good list of the things to pay attention to.

Looks like a nice tool to monitor your network.

Be sure to pick the right behavior model when you make a benchmark. Otherwise you might just measure the wrong thing.

Scary thread... developers should know better than do this and ship it on devices around the world. Their data is now anyone for the taking and users' privacy can't be ensured.