Angular2 application half in Typescript and Javascript

Question

I currently have a large JavaScript application with a lot of code written in vanilla Javascript for a specific platform for where I work.

I need to transform this into a web application I can open in the browser. This should be able to be done relatively easy by swapping out the components from my current application to the components of another web technology.

However since Angular2 is written in TypeScript, if I was to choose it as the framework I use, should I really also be rewriting the rest of my non-component JavaScript to TypeScript to or will I not need to do this.

Would it be a bad idea to have an application which was half TypeScript and half JavaScript like this?

Answer 1

It's not a bad idea to mix TypeScript and JavaScript. I do it every day. But you have to now that it may be very painful in some cases. So I can only advice to enforce migration to TypeScript as fast as possible.

I would suggest you to read this introduction to migration from JavaScript to TypeScript: https://www.typescriptlang.org/docs/handbook/migrating-from-javascript.html

This might also be a valuable source: https://basarat.gitbooks.io/typescript/content/docs/types/migrating.html but I have the impression that the author has a very narrow opinion on how to work with typescript so just don't take everything there as it is, but just as a suggestion.

There are also a lot of other resources about migrating from JavaScript to TypeScript.

For the last month of migration to TypeScript I can say, that in many cases you can simply change your JavaScript to a TypeScript file and add exports. Than you need to add the needed imports in the other places and everything works just like before.

If you can make sure, that you only use old JavaScript in your TypeScript and not the other way round you can split your project into to packages. Load the JavaScript into global as done before and than create Typings for the parts of your JavaScript you use in TypeScript.