helgihaf / TypescriptSurvival

My clumsy-but-essential tips and tricks for using Typescript

Typescript Survival

My clumsy-but-essential tips and tricks for using Typescript

var or let?

Use let.

arrays

Arrays are can be used as dynamic lists.

let list: number[] = [1, 2, 3];
let a = list[0];
list.push(7);
let listCopy = list.slice();

async / await

This traditional function with promises:

getTiersPromise(): Promise<Tier[]> {
  return this.http.get<Tier[]>(
    this.tierUrl + '/tiers').toPromise()
    .then(function (tiers: Tier[]) { return tiers.sort((a, b) => a.name < b.name ? -1 : (a.name > b.name ? 1 : 0)))
    .catch(function(err) {
      return null;
    });
} 

...is equal to this function using async / await:

async getTiers(): Promise<Tier[]> {
  try {
    let tiers = await this.http.get<Tier[]>(this.tierUrl + '/tiers').toPromise();
    return tiers.sort((a, b) => a.name < b.name ? -1 : (a.name > b.name ? 1 : 0));
  }
  catch (err) {
    return null;
  };
}

Consuming Web APIs (Angular 4 version)

import { HttpClient, HttpHeaders } from '@angular/common/http';
import 'rxjs/add/operator/toPromise';

//...

async getStuff() : Promise<Stuff[]> {
  let url = this.goCreateUrl();
  return await this.http.get<Stuff[]>(url,
      { headers: new HttpHeaders().set('apikey', 'asdf') }
    ).toPromise();
}