Scratch extension data URL, for https://scratch.mit.edu/users/Sheep_maker/#comments-123423617

README.md

I'm using the following localStorage extension:

importScripts('https://cdnjs.cloudflare.com/ajax/libs/localforage/1.7.3/localforage.min.js')

class LocalStorage {
  constructor () {}

  getInfo () {
    return {
      id: 'localstorage',
      name: 'LocalStorage',

      blocks: [
        {
          opcode: 'readLocalStorage',

          blockType: Scratch.BlockType.REPORTER,

          text: '[NAME]',
          arguments: {
            NAME: {
              type: Scratch.ArgumentType.STRING,
              defaultValue: 'highscore'
            }
          }
        },
        {
          opcode: 'setLocalStorage',

          blockType: Scratch.BlockType.COMMAND,

          text: 'set [NAME] to [VALUE]',
          arguments: {
            NAME: {
              type: Scratch.ArgumentType.STRING,
              defaultValue: 'highscore'
            },
            VALUE: {
              type: Scratch.ArgumentType.STRING,
              defaultValue: '12'
            }
          }
        }
      ]
    }
  }

  readLocalStorage ({ NAME }) {
    return localforage.getItem(NAME)
      .then(value => value || '')
  }

  setLocalStorage ({ NAME, VALUE }) {
    return localforage.setItem(NAME, VALUE)
  }
}

Scratch.extensions.register(new LocalStorage())

You can paste the following into the "Enter the URL of the extension" dialogue that pops up when you select "Choose an extension: For developers":

data:text/javascript;base64,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

Alternatively, you can URL settings editor (File > Change URL settings) to generate a URL like

https://sheeptester.github.io/scratch-gui/?extension=data%3Atext%2Fjavascript%3Bbase64%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%3D%3D

If loading an extension this way doesn't work, there might have been an error, which will appear in the console. You can look up how to open the browser console