Executing JavaScript code remotely on an open browser tab, whether from a file or as a JavaScript expression: How does it work?

Question

Executing JavaScript code remotely on an open browser tab, whether from a file or as a JavaScript expression: How does it work?

Is there a way to execute JavaScript on an already open browser tab remotely? For instance, if there is a tab open (of a webpage I do not manage) and I want to run a script within that specific tab by somehow sending the script from the command line.

The goal is to create the script in any IDE and then execute it in the context of an existing webpage.

Ideally, each execution would be isolated so that multiple evaluations of const someVar = 1 would not interfere with each other (since a const cannot be redefined).

javascript browser

Answer 1

Answer №1

To enable JavaScript debugging in Chromium based browsers, you can run the following commands remotely:

Start the browser:
```
chromium --remote-debugging-port=9222
```
Retrieve a list of open tabs:
```
curl -s -o - http://127.0.0.1:9222/json
```

Execute script on a specific page using Runtime.evaluate:

page_id=9EB553A6AE7860E5036BCE836258E22F 
code='(function() { console.log("Hello, console!"); return 42; })()'
jq -c -n \
  --arg code "$code" \
  '{id: 0, method: "Runtime.evaluate", "params":{expression: $code}}' \
     | websocat -t - "ws://127.0.0.1:9222/devtools/page/$page_id"

For the final step, ensure to send properly escaped JavaScript as a string within a JSON object. In this example, I'm utilizing jq and websocat, but other tools can also be used for the same purpose.

Answer 2

To enable JavaScript debugging in Chromium based browsers, you can run the following commands remotely:

Start the browser:
```
chromium --remote-debugging-port=9222
```
Retrieve a list of open tabs:
```
curl -s -o - http://127.0.0.1:9222/json
```

Execute script on a specific page using Runtime.evaluate:

page_id=9EB553A6AE7860E5036BCE836258E22F 
code='(function() { console.log("Hello, console!"); return 42; })()'
jq -c -n \
  --arg code "$code" \
  '{id: 0, method: "Runtime.evaluate", "params":{expression: $code}}' \
     | websocat -t - "ws://127.0.0.1:9222/devtools/page/$page_id"

For the final step, ensure to send properly escaped JavaScript as a string within a JSON object. In this example, I'm utilizing jq and websocat, but other tools can also be used for the same purpose.

Answer 3

Answer №2

Controlling computers remotely can be done in numerous ways, such as SSH, VNC, TeamViewer, NoMachine, and more. With the exception of SSH, these methods allow for graphical control, enabling users to interact with a remote browser through clicking and typing.

If you're looking to have users expose their computer to you, one option is to develop a browser plug-in that can make fetch requests to your server to retrieve code. However, it's important to note that browser plug-ins come with certain security restrictions that may impact your goals.

For example, there are limitations on what a plug-in can do within the developer console. While some manipulations are feasible, like with plug-ins such as React Developer Tools interacting with browser dev tools, further research is needed to understand these boundaries. Additionally, plug-ins have constraints when it comes to accessing the filesystem, although they can potentially influence it with user consent.

Answer 4

Controlling computers remotely can be done in numerous ways, such as SSH, VNC, TeamViewer, NoMachine, and more. With the exception of SSH, these methods allow for graphical control, enabling users to interact with a remote browser through clicking and typing.

If you're looking to have users expose their computer to you, one option is to develop a browser plug-in that can make fetch requests to your server to retrieve code. However, it's important to note that browser plug-ins come with certain security restrictions that may impact your goals.

For example, there are limitations on what a plug-in can do within the developer console. While some manipulations are feasible, like with plug-ins such as React Developer Tools interacting with browser dev tools, further research is needed to understand these boundaries. Additionally, plug-ins have constraints when it comes to accessing the filesystem, although they can potentially influence it with user consent.

Executing JavaScript code remotely on an open browser tab, whether from a file or as a JavaScript expression: How does it work?

Answer №1

Answer №2

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