How to run a JavaScript function in a Scratch project

samq64

For our example JavaScript function we will be creating a dialog box displaying the message “Hello world!”

alert("Hello world!");

Start by opening a new Scratch project and create these cloud variables:

(☁ eval)
(☁ eval output)
(☁ eval error)

The eval cloud variable is used to run the JavaScript function, the eval output cloud variable returns the output of the JavaScript function and the eval error cloud variable displays an error if there is one while running the JavaScript function. All three variables are required and must be be cloud variables and have the same names as above.

After you create your variables, check the boxes next to them to make the monitors appear on the stage.

Now create your simple script to display an alert dialog box:

when green flag clicked
set [☁ eval v] to [alert("Hello world!");]

If you click the green flag, nothing will happen, this is because your three variables are just normal cloud variables. To make it work, you first need to compile the project with Sheep_maker's HTMLifier.

Save the project to your computer and go to https://sheeptester.github.io/htmlifier

For your project source, choose “Upload project file” and select your project.

Change any other options you like, but make sure to keep the box that says “Give certain cloud variables special behaviours depending on the name?” checked.

Click “HTMLify!” and open the file after it's finished downloading.

If everything went well, you should see a dialog box displaying the message “Hello world!” and the variable monitors should look like this:

If not, check the “eval error” monitor to see what went wrong, then go back to your project, fix your errors and recompile it.

Notes

Since this doesn't work unless the project compiled with HTMlifier, you can't share it on the Scratch website. If you want to share your it with others, you'll need to host your it on your own website. (Or you can upload it onto a game site.) I recommend using GitHub Pages.

If you would like more information about JavaScript cloud variables and other special cloud variable behaviours using HTMLifier, then you can find more information here.

I am not an expert at JavaScript, so if you're having trouble with the scripts themselves, please don't ask here.

Other Things To Try

Displays a dialog with two buttons: OK and Cancel. returns true if OK was clicked and false if cancel was clicked.
```
confirm("Are you sure?");
```

Similar to the ask () and wait block, except it's a dialog box.
```
prompt("Enter your name:");
```

Changes the way the mouse cursor looks. A full list of cursors can be found here.
```
document.body.style.cursor = "pointer";
```

Last edited by samq64 (May 3, 2021 00:09:21)

Vaibhs11

Cool! Can it do browser js/DOM manipulation

samq64

Vaibhs11 wrote:
Cool! Can it do browser js/DOM manipulation

Well, it can change the mouse cursor, so yes, I think so.

Last edited by samq64 (May 2, 2021 19:30:09)

gosoccerboy5

Woahhh!

6d66yh

Is it possible to run Intel assembly this way?

samq64

6d66yh wrote:
Is it possible to run Intel assembly this way?

I don't know, I just read this the other day, and thought more Scratchers should know about it.

Last edited by samq64 (May 3, 2021 22:51:19)

airplanedodge

samq64 wrote:
Vaibhs11 wrote:
Cool! Can it do browser js/DOM manipulation
Well, it can change the mouse cursor, so yes, I think so.

!
there goes tolors thrown straight out the window

samq64

Bump

samq64

Bump

badstratch12

what da hell

DifferentDance8

airplanedodge wrote:
samq64 wrote:
Vaibhs11 wrote:
Cool! Can it do browser js/DOM manipulation
Well, it can change the mouse cursor, so yes, I think so.
!
there goes tolors thrown straight out the window

Then again, it only works on specific projects made using a specific compiler that's deprecated anyway and has no way of working on the official Scratch website, so I don't think this will affect TOLORS much.
=======
Cool! However, wouldn't this potentially be used to scrape Scratch session cookies and send it to some server and then hack your account? We've already had somewhat of a major problem a while ago where there was a fake tutorial going around on how to “beam” other accounts that (ironically enough) got your own account beamed

BigNate469

But

<!DOCTYPE html>
<html>
     <body>
          <script>
               // Insert JavaScript here
          </script>
     </body>
</html>

works…

Also, please don't post in old and inactive topics- this is known as necroposting.

Last edited by BigNate469 (May 29, 2024 15:11:21)

badstratch12

alert ('Hello World')

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