Your JavaScript is TypeScript

There were (and will continue to be) a lot of competitors in Some syntax to JavaScript compilers. TypeScript is different from them in that Your JavaScript is TypeScript. Here’s a diagram:

JavaScript is TypeScript

However it does mean that you need to learn JavaScript (the good news is you only need to learn JavaScript). TypeScript is just standardizing all the ways you provide good documentation on JavaScript.

  • Just giving you a new syntax doesn’t help fix bugs (looking at you CoffeeScript).
  • Creating a new language abstracts you too far from your runtimes, communities (looking at you Dart).

TypeScript is just JavaScript with docs.

Making JavaScript Better

TypeScript will try to protect you from portions of JavaScript that never worked (so you don’t need to remember this stuff):

  1. [] + []; // JavaScript will give you "" (which makes little sense), TypeScript will error
  3. //
  4. // other things that are nonsensical in JavaScript
  5. // - don't give a runtime error (making debugging hard)
  6. // - but TypeScript will give a compile time error (making debugging unnecessary)
  7. //
  8. {} + []; // JS : 0, TS Error
  9. [] + {}; // JS : "[object Object]", TS Error
  10. {} + {}; // JS : NaN or [object Object][object Object] depending upon browser, TS Error
  11. "hello" - 1; // JS : NaN, TS Error
  13. function add(a,b) {
  14.   return
  15.     a + b; // JS : undefined, TS Error 'unreachable code detected'
  16. }

Essentially TypeScript is linting JavaScript. Just doing a better job at it than other linters that don’t have type information.

You still need to learn JavaScript

That said TypeScript is very pragmatic about the fact that you do write JavaScript so there are some things about JavaScript that you still need to know in order to not be caught off-guard. Let’s discuss them next.

Note: TypeScript is a superset of JavaScript. Just with documentation that can actually be used by compilers / IDEs ;)