hacktricks/pentesting-web/xss-cross-site-scripting/debugging-client-side-js.md

# Debugging Client Side JS

## Debugging Client Side JS

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Debugging client side JS can be a pain because every-time you change the URL (including a change in the params used or param values) you need to **reset the breakpoint and reload the page**.

### `debugger;`

If you place the line `debugger;` inside a JS file, when the **browser** executes the JS it will **stop** the **debugger** in that place. Therefore, one way to set constant breakpoints would be to **download all the files locally and change set breakpoints in the JS code**.

### Overrides

Browser overrides allows to have a local copy of the code that is going to be executed and execute that one instead of the one from the remote server.\
You can **access the overrides** in "Dev Tools" --> "Sources" --> "Overrides".

You need to **create a local empty folder to be used to store the overrides**, so just create a new local folder and set is as override in that page.

Then, in "Dev Tools" --> "Sources" **select the file** you want to override and with **right click select "Save for overrides"**.

![](<../../.gitbook/assets/image (742).png>)

This will **copy the JS file locally** and you will be able to **modify that copy in the browser**. So just add the **`debugger;`** command wherever you want, **save** the change and **reload** the page, and every-time you access that web page **your local JS copy is going to be loaded** and your debugger command maintained in its place:

![](<../../.gitbook/assets/image (594).png>)

## References

* [https://www.youtube.com/watch?v=BW\_-RCo9lo8\&t=1529s](https://www.youtube.com/watch?v=BW\_-RCo9lo8\&t=1529s)

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Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)

<details>

<summary>Support HackTricks</summary>

* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.

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