Notes for typescript

notes.ts

// 1. Typed Tuple
let error: [number, string] = [123, 'Some Message'];

// Both correctly typed
let [code, message] = error;   // code is number and message is string
let anotherCode = error[0];    // anotherCode is number
let anotherMessage = error[1]; // anotherMessage is string

// 2. String Literal Type

class Socket {
    on (event: 'open' | 'message' | 'error' | 'close', cb) { // compiler errors when passed in string is not listed
        // ...
    }
}

let mySock = new Socket();
socket.on('message', () => {});

// 3. Void
function log(message: string): void {
    // ...
}

// If function does not return any value, we should mark its return type to void. Otherwise, it defaults to any.

// 4. Implements Class

class Base1 {
    method1 () {}
}
class Base2 {
    method2 () {}
}

class MyClass implements Base1, Base2 {
    constructor (private base1: Base1, private base2: Base2) {}
    method1 () { return this.base1.method1(); }
    method2 () { return this.base2.method2(); }
}