npm install --save-dev jest
npm install jest-environment-jsdom
npm run test

package.json
{
  "devDependencies": {
    "jest": "^29.7.0"
  },
  "scripts": {
    "test": "jest"
  },
  "jest": {
    "displayName": "Jest EisenR",
    "globals": {
      "PROJECT_NAME": "EisenRadio"
    },
    "bail": 20,
    "verbose": true
  }
}
https://kinsta.com/de/blog/jest/
https://dev.to/dstrekelj/series/13799
https://dev.to/dstrekelj/how-to-test-classes-with-jest-jif
https://www.meticulous.ai/blog/mocking-a-javascript-class-with-jest-two-ways-to-make-it-easier

ESlint support - Learned they can only work on one file, no var support of others, useless for a bigger project!
npm install --save-dev eslint
npm init @eslint/config
npx eslint eisenradio/eisenhome/bp_home_static/js/index.js