Getting to Know Typescript

Next: typescripts-type-system

1. Understand the Relationship Between Typescript and Javascript

Typescript is a superset of Javascript, with extra functionality:

We can annotate the type of a function like so:

function greet(who: string) {
  console.log("Hello", who);
}

Typescript has better error handling than javascript:

let city = "new york city";
console.log(city.toUppercase());

Will throw this error:

TypeError: city.toUppercase is not a function

Typescript’s type checker can spot the problem a little bit better:

let city = "new york city";
console.log(city.toUppercase());
// ~~~~~~~~~~~ Property 'toUppercase' does not exist on type
//             'string'. Did you mean 'toUpperCase'?

Next: typescripts-type-system