"Converting a Service Worker from JavaScript to TypeScript: A Step-by-Step

Scenario

I am in the process of converting my service-worker file from JavaScript to TypeScript in order to improve maintenance. Below is a snippet from my sw.js file:

/* eslint-disable no-console */
self.addEventListener("push", (event) => {
  ...
});
...more handlers

Issue

While I have made many changes to comply with TS and ESLint requirements, I am facing an issue with the usage of self. ESLint is flagging two errors:

unexpected use of 'self' 
self is not defined

How can I properly define 'self' in a TypeScript file?

typescripteslintservice-worker

Answer №1

Adding the webworker library to the tsconfig.json file is necessary.

{
 ....
  "compilerOptions": {
  "lib": [
    ...
    "webworker"
  ],...
}

Once the webworker library is added, you can declare self with typescript using ServiceWorkerGlobalScope.

The ServiceWorkerGlobalScope interface represents the global execution context of a service worker in the ServiceWorker API.

declare const self: ServiceWorkerGlobalScope;

If the isolatedModules flag is set to true in your tsconfig.json, you will need to add import or export directives to your service worker file.

Typescript considers files without import/exports as legacy script files, which are not modules and have their definitions merged in the global namespace. The isolatedModules flag prevents such files.

If no import or export is needed, the easiest way to make a file a module is to add export { }; here's a stack question explaining this issue

Ultimately, you can utilize full typescript syntax in the sw.ts file.

Answer №2

It is possible to include the webworker library in your sw.ts file.

/// <reference lib="webworker" />
declare let self: ServiceWorkerGlobalScope;

self.addEventListener('install', () => {
  // perform some action here
});

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