How can you use the memory panel in browser developer tools to debug web application memory leaks?

1 What is the memory panel?

The memory panel is a feature of browser developer tools that allows you to inspect the memory heap of your web application. The memory heap is where the browser stores all the objects, variables, functions, and other data that your web application needs to run. The memory panel can show you how much memory your web application is using, how it is distributed among different types of objects, and how it changes over time. You can use the memory panel to identify memory leaks, compare snapshots, and isolate sources of memory allocation.

2 How to access the memory panel?

To access the memory panel, you need to open the browser developer tools first. You can do this by pressing F12 or Ctrl+Shift+I on Windows, or Cmd+Option+I on Mac. Alternatively, you can right-click on any element of your web page and select Inspect. Once the developer tools are open, you can switch to the memory panel by clicking on the Memory tab. Depending on your browser, the memory panel may have different subtabs, such as Heap Snapshot, Allocation Timeline, Allocation Instrumentation, or Memory Problems.

3 How to take a memory snapshot?

A memory snapshot is a snapshot of the memory heap at a given moment. It shows you all the objects that are currently in memory, their sizes, and their references. You can take a memory snapshot by clicking on the Take Snapshot button in the memory panel. This will pause your web application and capture the state of the memory heap. You can then inspect the snapshot by using the filters, search, and sorting options in the memory panel. You can also compare two snapshots by selecting them and clicking on the Comparison view.

4 How to record a memory timeline?

A memory timeline is a recording of the memory heap over a period of time. It shows you how the memory usage of your web application changes as it runs, and how often it performs garbage collection. Garbage collection is the process of freeing up memory by removing unused objects. You can record a memory timeline by clicking on the Record button in the memory panel. This will start recording the memory heap as your web application runs. You can then stop the recording by clicking on the Stop button. You can then analyze the timeline by using the zoom, filter, and hover options in the memory panel.

5 How to detect a memory leak?

A memory leak is a situation where your web application retains objects that are no longer needed, preventing the browser from reclaiming their memory. This can cause your web application to consume more and more memory over time, leading to performance issues or crashes. You can detect a memory leak by using the memory panel in two ways: by taking multiple snapshots and comparing them, or by recording a memory timeline and looking for patterns.

To use the snapshot method, you need to take a snapshot of the memory heap before and after performing an action in your web application, such as loading a page, clicking a button, or navigating a menu. Then, you need to compare the two snapshots and look for objects that have increased in size or number, and that are not expected to be in memory. These objects may indicate a memory leak, and you can trace their references to find out where they are created and retained.

To use the timeline method, you need to record a memory timeline for a few minutes while performing various actions in your web application. Then, you need to look for patterns in the timeline that show a steady or sudden increase in memory usage, without a corresponding decrease after garbage collection. These patterns may indicate a memory leak, and you can zoom in and hover over the timeline to see the details of the memory allocation and deallocation events.

6 How to fix a memory leak?

Fixing a memory leak can be difficult, as it can have various causes, such as global variables, closures, event listeners, timers, or circular references. To help you fix a memory leak, review your code and look for places where you create and store objects. Make sure to delete or nullify any references to objects that are no longer needed. Additionally, use the delete operator to remove properties from objects that are no longer needed, or use the WeakMap or WeakSet data structures to store objects that can be garbage collected when they are not referenced elsewhere. Remove any event listeners or timers that are not needed anymore, or use the once option to make them fire only once. It is also important to avoid circular references by using weak references or deleting or nullifying one of the references. Following these steps can help you fix a memory leak and improve your code's performance.

7 Here’s what else to consider

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