Angular code explainers

typescript

import { Directive, ElementRef, HostListener, Input, OnDestroy, OnInit } from '@angular/core';
 
@Directive({
  selector: '[appTrapFocus]',

Building a focus-trap directive in Angular

accessibility focus-management dom

Intermediate 9 steps

typescript

import { inject } from '@angular/core';
import {
  CanActivateFn,
  Router,

Functional route guards in Angular

route-guards dependency-injection observables

Intermediate 5 steps

typescript

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import {
  AsyncValidator,

How an async username validator works in Angular

async-validation reactive-forms rxjs

Intermediate 6 steps

typescript

import {
  Directive,
  Input,
  TemplateRef,

Building a structural *appUnless directive in Angular

structural-directive template-rendering dependency-injection

Intermediate 8 steps

typescript

import { inject } from '@angular/core';
import { ResolveFn, Router, ActivatedRouteSnapshot } from '@angular/router';
import { catchError, of, EMPTY } from 'rxjs';
import { Article } from './models/article';

Prefetching route data with an Angular resolver

route-resolver dependency-injection rxjs

Intermediate 6 steps

typescript

import { Pipe, PipeTransform, ChangeDetectorRef, NgZone, OnDestroy } from '@angular/core';
 
@Pipe({
  name: 'timeAgo',

A self-refreshing timeAgo pipe in Angular

impure-pipe change-detection timers

Advanced 10 steps

typescript

import { Component } from '@angular/core';
import { FormControl, ReactiveFormsModule } from '@angular/forms';
import { HttpClient } from '@angular/common/http';
import { AsyncPipe } from '@angular/common';

Reactive type-ahead search in Angular

rxjs reactive-forms debounce

Intermediate 9 steps

typescript

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable, throwError, timer } from 'rxjs';
import { mergeMap, retryWhen } from 'rxjs/operators';

Exponential backoff retries in Angular

retry exponential-backoff rxjs

Advanced 7 steps

typescript

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable, shareReplay } from 'rxjs';

Caching HTTP config in an Angular service

caching observables dependency-injection

Intermediate 6 steps