Angular vs Svelte 4 Comparison

Reactivity

Declare state

Angular

import { Component, NgModule } from "@angular/core";

@Component({
  selector: "app-name",
  template: `<h1>Hello {{ name }}</h1>`,
})
export class NameComponent {
  name = "John";
}

@NgModule({
  declarations: [NameComponent],
  exports: [NameComponent],
})
export class NameModule {}

Svelte 4

<script>
  let name = "John";
</script>

<h1>Hello {name}</h1>

Update state

Angular

import { Component, NgModule } from "@angular/core";

@Component({
  selector: "app-name",
  template: `<h1>Hello {{ name }}</h1>`,
})
export class NameComponent {
  name = "John";

  constructor() {
    this.name = "Jane";
  }
}

@NgModule({
  declarations: [NameComponent],
  exports: [NameComponent],
})
export class NameModule {}

Svelte 4

<script>
  let name = "John";
  name = "Jane";
</script>

<h1>Hello {name}</h1>

Computed state

Angular

import { Component, NgModule } from "@angular/core";

@Component({
  selector: "app-doublecount",
  template: `<div>{{ doubleCount }}</div>`,
})
export class DoublecountComponent {
  count = 10;

  get doubleCount() {
    return this.count * 2;
  }
}

@NgModule({
  declarations: [DoublecountComponent],
  exports: [DoublecountComponent],
})
export class DoublecountModule {}

Svelte 4

<script>
  let count = 10;
  $: doubleCount = count * 2;
</script>

<div>{doubleCount}</div>

Templating

Minimal template

Angular

import { Component, NgModule } from "@angular/core";

@Component({
  selector: "app-helloworld",
  template: `<h1>Hello world</h1>`,
})
export class HelloworldComponent {}

@NgModule({
  declarations: [HelloworldComponent],
  exports: [HelloworldComponent],
})
export class HelloworldModule {}

Svelte 4

<h1>Hello world</h1>

Styling

Angular

import { Component, NgModule } from "@angular/core";

@Component({
  selector: "app-cssstyle",
  template: `
    <h1 class="title">I am red</h1>
    <button style="font-size: 10rem">I am a button</button>
  `,
  styles: [
    `
      .title {
        color: red;
      }
    `,
  ],
})
export class CssStyleComponent {}

@NgModule({
  declarations: [CssStyleComponent],
  exports: [CssStyleComponent],
})
export class CssStyleModule {}

Svelte 4

<h1 class="title">I am red</h1>
<button style="font-size: 10rem;">I am a button</button>

<style>
  .title {
    color: red;
  }
</style>

Loop

Angular

import { Component, NgModule } from "@angular/core";
import { CommonModule } from "@angular/common";

@Component({
  selector: "app-colors",
  template: `
    <ul>
      <li *ngFor="let color of colors">{{ color }}</li>
    </ul>
  `,
})
export class ColorsComponent {
  colors = ["red", "green", "blue"];
}

@NgModule({
  declarations: [ColorsComponent],
  imports: [CommonModule],
  exports: [ColorsComponent],
})
export class ColorsModule {}

Svelte 4

<script>
  const colors = ["red", "green", "blue"];
</script>

<ul>
  {#each colors as color (color)}
    <li>{color}</li>
  {/each}
</ul>

Event click

Angular

import { Component, NgModule } from "@angular/core";

@Component({
  selector: "app-counter",
  template: `
    <p>Counter: {{ count }}</p>
    <button (click)="incrementCount()">+1</button>
  `,
})
export class CounterComponent {
  count = 0;

  incrementCount() {
    this.count++;
  }
}

@NgModule({
  declarations: [CounterComponent],
  exports: [CounterComponent],
})
export class CounterModule {}

Svelte 4

<script>
  let count = 0;

  function incrementCount() {
    count++;
  }
</script>

<p>Counter: {count}</p>
<button on:click={incrementCount}>+1</button>

Dom ref

Angular

import {
  Component,
  ViewChild,
  ElementRef,
  OnInit,
  NgModule,
} from "@angular/core";

@Component({
  selector: "app-inputfocused",
  template: `<input type="text" #inputRef />`,
})
export class InputfocusedComponent implements OnInit {
  @ViewChild("inputRef", { static: true })
  inputRef!: ElementRef<HTMLInputElement>;

  ngOnInit() {
    this.inputRef.nativeElement.focus();
  }
}

@NgModule({
  declarations: [InputfocusedComponent],
  exports: [InputfocusedComponent],
})
export class InputfocusedModule {}

Svelte 4

<script>
  import { onMount } from "svelte";

  let inputElement;

  onMount(() => {
    inputElement.focus();
  });
</script>

<input bind:this={inputElement} />

Conditional

Angular

import { Component, NgModule } from "@angular/core";
import { CommonModule } from "@angular/common";

const TRAFFIC_LIGHTS = ["red", "orange", "green"];

@Component({
  selector: "app-trafficlight",
  template: `
    <button (click)="nextLight()">Next light</button>
    <p>Light is: {{ light }}</p>
    <p>
      You must
      <ng-container [ngSwitch]="light">
        <span *ngSwitchCase="'red'">STOP</span>
        <span *ngSwitchCase="'orange'">SLOW DOWN</span>
        <span *ngSwitchCase="'green'">GO</span>
      </ng-container>
    </p>
  `,
})
export class TrafficlightComponent {
  lightIndex = 0;

  get light() {
    return TRAFFIC_LIGHTS[this.lightIndex];
  }

  nextLight() {
    this.lightIndex = (this.lightIndex + 1) % TRAFFIC_LIGHTS.length;
  }
}

@NgModule({
  declarations: [TrafficlightComponent],
  imports: [CommonModule],
  exports: [TrafficlightComponent],
})
export class TrafficlightModule {}

Svelte 4

<script>
  const TRAFFIC_LIGHTS = ["red", "orange", "green"];
  let lightIndex = 0;

  $: light = TRAFFIC_LIGHTS[lightIndex];

  function nextLight() {
    lightIndex = (lightIndex + 1) % TRAFFIC_LIGHTS.length;
  }
</script>

<button on:click={nextLight}>Next light</button>
<p>Light is: {light}</p>
<p>
  You must
  {#if light === "red"}
    <span>STOP</span>
  {:else if light === "orange"}
    <span>SLOW DOWN</span>
  {:else if light === "green"}
    <span>GO</span>
  {/if}
</p>

Lifecycle

On mount

Angular

import { Component, NgModule, OnInit } from "@angular/core";

@Component({
  selector: "app-pagetitle",
  template: `<p>Page title: {{ pageTitle }}</p>`,
})
export class PagetitleComponent implements OnInit {
  pageTitle = "";

  ngOnInit() {
    this.pageTitle = document.title;
  }
}

@NgModule({
  declarations: [PagetitleComponent],
  exports: [PagetitleComponent],
})
export class PagetitleModule {}

Svelte 4

<script>
  import { onMount } from "svelte";
  let pageTitle = "";
  onMount(() => {
    pageTitle = document.title;
  });
</script>

<p>Page title: {pageTitle}</p>

On unmount

Angular

import { Component, NgModule, OnDestroy } from "@angular/core";

@Component({
  selector: "app-time",
  template: `<p>Current time: {{ time }}</p>`,
})
export class TimeComponent implements OnDestroy {
  time = new Date().toLocaleTimeString();

  timer = setInterval(() => {
    this.time = new Date().toLocaleTimeString();
  }, 1000);

  ngOnDestroy() {
    clearInterval(this.timer);
  }
}

@NgModule({
  declarations: [TimeComponent],
  exports: [TimeComponent],
})
export class TimeModule {}

Svelte 4

<script>
  import { onDestroy } from "svelte";

  let time = new Date().toLocaleTimeString();

  const timer = setInterval(() => {
    time = new Date().toLocaleTimeString();
  }, 1000);

  onDestroy(() => clearInterval(timer));
</script>

<p>Current time: {time}</p>

Component composition

Props

Angular

import { Component, NgModule } from "@angular/core";
import { UserprofileModule } from "./userprofile.component";

@Component({
  selector: "app-root",
  template: `
    <app-userprofile
      name="John"
      [age]="20"
      [favouriteColors]="['green', 'blue', 'red']"
      [isAvailable]="true"
    >
    </app-userprofile>
  `,
})
export class AppComponent {}

@NgModule({
  declarations: [AppComponent],
  imports: [UserprofileModule],
  bootstrap: [AppComponent],
})
export class AppModule {}

Svelte 4

<script>
  import UserProfile from "./UserProfile.svelte";
</script>

<UserProfile
  name="John"
  age={20}
  favouriteColors={["green", "blue", "red"]}
  isAvailable
/>

Emit to parent

Angular

import { Component, NgModule } from "@angular/core";
import { AnswerButtonModule } from "./answer-button.component";

@Component({
  selector: "app-root",
  template: `
    <p>Are you happy?</p>

    <app-answer-button (yes)="onAnswerYes()" (no)="onAnswerNo()">
    </app-answer-button>

    <p style="font-size: 50px">{{ isHappy ? "😀" : "😥" }}</p>
  `,
})
export class AppComponent {
  isHappy = true;

  onAnswerYes() {
    this.isHappy = true;
  }

  onAnswerNo() {
    this.isHappy = false;
  }
}

@NgModule({
  declarations: [AppComponent],
  imports: [AnswerButtonModule],
  bootstrap: [AppComponent],
})
export class AppModule {}

Svelte 4

<script>
  import AnswerButton from "./AnswerButton.svelte";

  let isHappy = true;

  function onAnswerNo() {
    isHappy = false;
  }

  function onAnswerYes() {
    isHappy = true;
  }
</script>

<p>Are you happy?</p>
<AnswerButton on:yes={onAnswerYes} on:no={onAnswerNo} />
<p style="font-size: 50px;">{isHappy ? "😀" : "😥"}</p>

Slot

Angular

import { Component, NgModule } from "@angular/core";
import { FunnyButtonModule } from "./funny-button.component";

@Component({
  selector: "app-root",
  template: `<app-funny-button>Click me!</app-funny-button>`,
})
export class AppComponent {}

@NgModule({
  declarations: [AppComponent],
  imports: [FunnyButtonModule],
  bootstrap: [AppComponent],
})
export class AppModule {}

Svelte 4

<script>
  import FunnyButton from "./FunnyButton.svelte";
</script>

<FunnyButton>Click me!</FunnyButton>

Slot fallback

Angular

import { Component, NgModule } from "@angular/core";

@Component({
  selector: "app-root",
  template: `
    <app-funny-button></app-funny-button>

    <app-funny-button>
      <ng-template #content>I got content!</ng-template>
    </app-funny-button>
  `,
})
export class AppComponent {}

@NgModule({
  declarations: [AppComponent],
  imports: [FunnyButtonModule],
  bootstrap: [AppComponent],
})
export class AppModule {}

Svelte 4

<script>
  import FunnyButton from "./FunnyButton.svelte";
</script>

<FunnyButton />
<FunnyButton>I got content!</FunnyButton>

Context

Angular

import { Component, NgModule } from "@angular/core";
import { UserService } from "./user.service";
import { UserProfileModule } from "./user-profile.component";

@Component({
  providers: [UserService],
  selector: "app-root",
  template: `
    <h1>Welcome back, {{ userService.user.username }}</h1>
    <app-user-profile />
  `,
})
export class AppComponent {
  constructor(public userService: UserService) {}
}

@NgModule({
  declarations: [AppComponent],
  imports: [UserProfileModule],
  bootstrap: [AppComponent],
})
export class AppModule {}

Svelte 4

<script>
  import { setContext } from "svelte";
  import UserProfile from "./UserProfile.svelte";
  import createUserStore from "./createUserStore.js";

  const userStore = createUserStore({
    id: 1,
    username: "unicorn42",
    email: "unicorn42@example.com",
  });

  setContext("user", userStore);
</script>

<h1>Welcome back, {$userStore.username}</h1>
<UserProfile />

Form input

Input text

Angular

import { Component, NgModule } from "@angular/core";
import { FormsModule } from "@angular/forms";

@Component({
  selector: "app-input-hello",
  template: `
    <p>{{ text }}</p>
    <input [(ngModel)]="text" />
  `,
})
export class InputHelloComponent {
  text = "";
}

@NgModule({
  declarations: [InputHelloComponent],
  imports: [FormsModule],
  exports: [InputHelloComponent],
})
export class InputHelloModule {}

Svelte 4

<script>
  let text = "Hello World";
</script>

<p>{text}</p>
<input bind:value={text} />

Checkbox

Angular

import { Component, NgModule } from "@angular/core";
import { FormsModule } from "@angular/forms";

@Component({
  selector: "app-is-available",
  template: `
    <input id="is-available" type="checkbox" [(ngModel)]="isAvailable" />
    <label for="is-available">Is available</label>
  `,
})
export class IsAvailableComponent {
  isAvailable = false;
}

@NgModule({
  declarations: [IsAvailableComponent],
  imports: [FormsModule],
  exports: [IsAvailableComponent],
})
export class IsAvailableModule {}

Svelte 4

<script>
  let isAvailable = false;
</script>

<input id="is-available" type="checkbox" bind:checked={isAvailable} />
<label for="is-available">Is available</label>

Radio

Angular

import { Component, NgModule } from "@angular/core";
import { FormsModule } from "@angular/forms";

@Component({
  selector: "app-pick-pill",
  template: `
    <div>Picked: {{ picked }}</div>

    <input id="blue-pill" type="radio" value="blue" [(ngModel)]="picked" />
    <label for="blue-pill">Blue pill</label>

    <input id="red-pill" type="radio" value="red" [(ngModel)]="picked" />
    <label for="red-pill">Red pill</label>
  `,
})
export class PickPillComponent {
  picked = "red";
}

@NgModule({
  declarations: [PickPillComponent],
  imports: [FormsModule],
  exports: [PickPillComponent],
})
export class PickPillModule {}

Svelte 4

<script>
  let picked = "red";
</script>

<div>Picked: {picked}</div>

<input id="blue-pill" bind:group={picked} type="radio" value="blue" />
<label for="blue-pill">Blue pill</label>

<input id="red-pill" bind:group={picked} type="radio" value="red" />
<label for="red-pill">Red pill</label>

Select

Angular

import { Component, NgModule } from "@angular/core";
import { FormsModule } from "@angular/forms";

@Component({
  selector: "app-color-select",
  template: `
    <select [(ngModel)]="selectedColorId">
      <option
        *ngFor="let color of colors"
        [value]="color.id"
        [disabled]="color.isDisabled"
      >
        {{ color.text }}
      </option>
    </select>
  `,
})
export class ColorSelectComponent {
  selectedColorId = 2;

  colors = [
    { id: 1, text: "red" },
    { id: 2, text: "blue" },
    { id: 3, text: "green" },
    { id: 4, text: "gray", isDisabled: true },
  ];
}

@NgModule({
  declarations: [ColorSelectComponent],
  imports: [FormsModule],
  exports: [ColorSelectComponent],
})
export class ColorSelectModule {}

Svelte 4

<script>
  let selectedColorId = 2;

  const colors = [
    { id: 1, text: "red" },
    { id: 2, text: "blue" },
    { id: 3, text: "green" },
    { id: 4, text: "gray", isDisabled: true },
  ];
</script>

<select bind:value={selectedColorId}>
  {#each colors as color}
    <option value={color.id} disabled={color.isDisabled}>
      {color.text}
    </option>
  {/each}
</select>

Webapp features

Render app

Angular

<!DOCTYPE html>
<html>
  <body>
    <app-root></app-root>
  </body>
</html>

Svelte 4

<!DOCTYPE html>
<html>
  <body>
    <div id="app"></div>
    <script type="module" src="./app.js"></script>
  </body>
</html>

Fetch data

Angular

import { HttpClient } from "@angular/common/http";
import { Injectable } from "@angular/core";
import { BehaviorSubject } from "rxjs";

export interface UsersState {
  users: User[];
  error: string | null;
  loading: boolean;
}

export const initialState: UsersState = {
  users: [],
  error: null,
  loading: false,
};

@Injectable({ providedIn: "root" })
export class UserService {
  private state = new BehaviorSubject<UsersState>(initialState);
  state$ = this.state.asObservable();

  constructor(private http: HttpClient) {}

  loadUsers() {
    this.state.next({ ...initialState, loading: true });

    this.http
      .get<UserResponse>("https://randomuser.me/api/?results=3")
      .subscribe({
        next: ({ results }) =>
          this.state.next({ ...initialState, users: results }),
        error: (error) => this.state.next({ ...initialState, error }),
      });
  }
}

export interface UserResponse {
  results: User[];
  info: any;
}

export interface User {
  name: {
    title: string;
    first: string;
    last: string;
  };
  picture: {
    large: string;
    medium: string;
    thumbnail: string;
  };
}

Svelte 4

<script>
  import useFetchUsers from "./useFetchUsers";

  const { isLoading, error, data: users } = useFetchUsers();
</script>

{#if $isLoading}
  <p>Fetching users...</p>
{:else if $error}
  <p>An error occurred while fetching users</p>
{:else if $users}
  <ul>
    {#each $users as user}
      <li>
        <img src={user.picture.thumbnail} alt="user" />
        <p>
          {user.name.first}
          {user.name.last}
        </p>
      </li>
    {/each}
  </ul>
{/if}

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