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:

However it does mean that you need to learn JavaScript (the good new 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 bug (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):

[] + []; // JavaScript will give you "" (which makes little sense), TypeScript will error

//
// other things that are nonsensical in JavaScript but don't give an error (but TypeScript will)
//
{} + []; // JS : "[Object object]", TS Error  
[] + {}; // JS : 0, TS Error  
{} + {}; // JS : NaN, TS Error
"hello" - 1; // JS : NaN, TS Error

Essentailly TypeScript is linting JavaScript. Just doing a better job at it then 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. Lets discuss them next.