Angular Renaissance vs Lit Comparison

Reactivity

Declare state

Angular Renaissance

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("x-name")
export class XName extends LitElement {
  @state()
  name = "John";

  render() {
    return html`<h1>Hello ${this.name}!</h1>`;
  }
}

Update state

Angular Renaissance

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

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("x-name")
export class XName extends LitElement {
  @state()
  name = "John";

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

  render() {
    return html`<h1>Hello ${this.name}!</h1>`;
  }
}

Computed state

Angular Renaissance

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

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

  doubleCount = computed(() => this.count() * 2);
}

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("double-count")
export class DoubleCount extends LitElement {
  @state()
  count = 10;

  render() {
    const doubleCount = this.count * 2;
    return html`<div>${doubleCount}</div>`;
  }
}

Templating

Minimal template

Angular Renaissance

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

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

Lit

import { LitElement, html } from "lit";
import { customElement } from "lit/decorators.js";

@customElement("hello-world")
export class HelloWorld extends LitElement {
  render() {
    return html`<h1>Hello world</h1>`;
  }
}

Styling

Angular Renaissance

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

@Component({
  selector: "app-css-style",
  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 {}

Lit

import { LitElement, html, css } from "lit";
import { customElement } from "lit/decorators.js";
import { styleMap } from "lit/directives/style-map.js";

@customElement("css-style")
export class CssStyle extends LitElement {
  static styles = css`
    .title {
      color: red;
    }
  `;

  render() {
    return html`
      <h1 class="title">I am red</h1>
      <button style=${styleMap({ fontSize: "10rem" })}>I am a button</button>
    `;
  }
}

Loop

Angular Renaissance

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

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

Lit

import { LitElement, html } from "lit";
import { customElement } from "lit/decorators.js";
import { repeat } from "lit/directives/repeat.js";

@customElement("colors-list")
export class ColorsList extends LitElement {
  colors = ["red", "green", "blue"];

  render() {
    return html`
      <ul>
        ${repeat(
          this.colors,
          (color) => color,
          (color) => html`<li>${color}</li>`
        )}
      </ul>
    `;
  }
}

Event click

Angular Renaissance

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

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

  incrementCount() {
    this.count.update((count) => count + 1);
  }
}

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("x-counter")
export class XCounter extends LitElement {
  @state()
  count = 0;

  incrementCount() {
    this.count = this.count + 1;
  }

  render() {
    return html`
      <p>Counter: ${this.count}</p>
      <button @click=${this.incrementCount}>+1</button>
    `;
  }
}

DOM ref

Angular Renaissance

import {
  afterNextRender,
  Component,
  ElementRef,
  viewChild,
} from "@angular/core";

@Component({
  selector: "app-input-focused",
  template: `<input type="text" #inputRef />`,
})
export class InputFocusedComponent {
  inputRef = viewChild.required<ElementRef<HTMLInputElement>>("inputRef");

  constructor() {
    afterNextRender({ write: () => this.inputRef().nativeElement.focus() });
  }
}

Lit

import { LitElement, html } from "lit";
import { customElement, state, query } from "lit/decorators.js";

@customElement("input-focused")
export class InputFocused extends LitElement {
  @query("input") inputEl;

  firstUpdated() {
    this.inputEl.focus();
  }

  render() {
    return html`<input type="text" />`;
  }
}

Conditional

Angular Renaissance

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

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

@Component({
  selector: "app-traffic-light",
  template: `
    <button (click)="nextLight()">Next light</button>
    <p>Light is: {{ light() }}</p>
    <p>
      You must @switch (light()) { @case ("red") {
      <span>STOP</span>
      } @case ("orange") {
      <span>SLOW DOWN</span>
      } @case ("green") {
      <span>GO</span>
      } }
    </p>
  `,
})
export class TrafficLightComponent {
  lightIndex = signal(0);

  light = computed(() => TRAFFIC_LIGHTS[this.lightIndex()]);

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";
import { choose } from "lit/directives/choose.js";

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

@customElement("traffic-light")
export class TrafficLight extends LitElement {
  @state()
  lightIndex = 0;

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

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

  render() {
    return html`
      <button @click=${this.nextLight}>Next light</button>
      <p>Light is ${this.light}</p>
      <p>
        You must ${choose(this.light, [
          ["red", () => html`<span>STOP</span>`],
          ["orange", () => html`<span>SLOW DOWN</span>`],
          ["green", () => html`<span>GO</span>`],
        ])}
      </p>
    `;
  }
}

Lifecycle

On mount

Angular Renaissance

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

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("page-title")
export class PageTitle extends LitElement {
  @state()
  pageTitle = "";

  connectedCallback() {
    super.connectedCallback();
    this.pageTitle = document.title;
  }

  render() {
    return html`<p>Page title: ${this.pageTitle}</p>`;
  }
}

On unmount

Angular Renaissance

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

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

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("x-time")
export class XTime extends LitElement {
  @state()
  time = "";

  timer;

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

  disconnectedCallback() {
    super.disconnectedCallback();
    clearInterval(this.timer);
  }

  render() {
    return html`<p>Current time: ${this.time}</p>`;
  }
}

Component composition

Props

Angular Renaissance

import { Component } from "@angular/core";
import { UserprofileComponent } from "./userprofile.component";

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

Lit

import { LitElement, html } from "lit";
import { customElement } from "lit/decorators.js";

import "./user-profile";

@customElement("x-app")
export class XApp extends LitElement {
  render() {
    return html`<user-profile
      name="John"
      age="20"
      .favouriteColors=${["green", "blue", "red"]}
      isAvailable
    ></user-profile>`;
  }
}

Emit to parent

Angular Renaissance

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

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

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

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

  onAnswerYes() {
    this.isHappy.set(true);
  }

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

import "./answer-button";

@customElement("x-app")
export class XApp extends LitElement {
  @state()
  isHappy = true;

  onAnswerNo() {
    this.isHappy = false;
  }

  onAnswerYes() {
    this.isHappy = true;
  }

  render() {
    return html`
      <p>Are you happy?</p>
      <answer-button
        @yes=${this.onAnswerYes}
        @no=${this.onAnswerNo}
      ></answer-button>
      <p style="font-size: 50px;">${this.isHappy ? "😀" : "😥"}</p>
    `;
  }
}

Slot

Angular Renaissance

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

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

Lit

import { LitElement, html } from "lit";
import { customElement } from "lit/decorators.js";

import "./funny-button";

@customElement("x-app")
export class XApp extends LitElement {
  render() {
    return html`<funny-button>Click me!</funny-button>`;
  }
}

Slot fallback

Angular Renaissance

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

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

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

Lit

import { LitElement, html } from "lit";
import { customElement } from "lit/decorators.js";

import "./funny-button";

@customElement("x-app")
export class XApp extends LitElement {
  render() {
    return html`
      <funny-button></funny-button>
      <funny-button>Click me!</funny-button>
    `;
  }
}

Context

Angular Renaissance

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";
import { ContextProvider } from "@lit/context";

import { userContext } from "./user-context";

import "./user-profile";

@customElement("x-app")
export class XApp extends LitElement {
  @state()
  user = {
    id: 1,
    username: "unicorn42",
    email: "unicorn42@example.com",
  };

  provider = new ContextProvider(this, {
    context: userContext,
    initialValue: this.user,
  });

  updateUsername(newUsername) {
    this.user = { ...this.user, username: newUsername };
    this.provider.setValue(this.user);
  }

  render() {
    return html` <h1>Welcome back, ${this.user.username}</h1>
      <user-profile
        .user="${this.user}"
        .updateUsername=${this.updateUsername.bind(this)}
      ></user-profile>`;
  }
}

Form input

Input text

Angular Renaissance

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("input-hello")
export class InputHello extends LitElement {
  @state()
  text = "Hello World";

  handleInput(event) {
    this.text = event.target.value;
  }

  render() {
    return html`
      <p>${this.text}</p>
      <input value=${this.text} @input=${this.handleInput} />
    `;
  }
}

Checkbox

Angular Renaissance

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("is-available")
export class IsAvailable extends LitElement {
  @state()
  isAvailable = false;

  handleChange() {
    this.isAvailable = !this.isAvailable;
  }

  render() {
    return html`
      <input
        id="is-available"
        type="checkbox"
        ?checked=${this.isAvailable}
        @change=${this.handleChange}
      />
      <label for="is-available">Is available</label>
    `;
  }
}

Radio

Angular Renaissance

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

@Component({
  imports: [FormsModule],
  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 = signal("red");
}

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";

@customElement("pick-pill")
export class PickPill extends LitElement {
  @state()
  picked = "red";

  handleChange(event) {
    this.picked = event.target.value;
  }

  render() {
    return html`
      <div>Picked: ${this.picked}</div>

      <input
        id="blue-pill"
        name="pill"
        ?checked=${this.picked === "blue"}
        type="radio"
        value="blue"
        @change=${this.handleChange}
      />
      <label for="blue-pill">Blue pill</label>

      <input
        id="red-pill"
        name="pill"
        ?checked=${this.picked === "red"}
        type="radio"
        value="red"
        @change=${this.handleChange}
      />
      <label for="red-pill">Red pill</label>
    `;
  }
}

Select

Angular Renaissance

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

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

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

Lit

import { LitElement, html } from "lit";
import { customElement, state } from "lit/decorators.js";
import { repeat } from "lit/directives/repeat";

@customElement("color-select")
export class ColorSelect extends LitElement {
  colors = [
    { id: 1, text: "red" },
    { id: 2, text: "blue" },
    { id: 3, text: "green" },
    { id: 4, text: "gray", isDisabled: true },
  ];

  @state()
  selectedColorId = 2;

  handleChange(event) {
    this.selectedColorId = event.target.value;
  }

  render() {
    return html`
      <select @change=${this.handleChange}>
        ${repeat(
          this.colors,
          (color) => color.id,
          (color) =>
            html`<option
              value=${color.id}
              ?selected=${this.selectedColorId === color.id}
              ?disabled=${color.isDisabled}
            >
              ${color.text}
            </option>`
        )}
      </select>
    `;
  }
}

Webapp features

Render app

Angular Renaissance

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

Lit

<!DOCTYPE html>
<html>
  <head>
    <script type="module" src="./app.js"></script>
  </head>

  <body>
    <x-app />
  </body>
</html>

Fetch data

Angular Renaissance

import { HttpClient } from "@angular/common/http";
import { inject, Injectable, signal } from "@angular/core";

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 http = inject(HttpClient);

  #state = signal<UsersState>(initialState);
  state = this.#state.asReadonly();

  loadUsers() {
    this.#state.update((state) => ({ ...state, loading: true }));

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

Lit

import { LitElement, html } from "lit";
import { customElement } from "lit/decorators.js";
import { createFetchUsersTask } from "./fetch-users-task";

@customElement("x-app")
export class XApp extends LitElement {
  fetchUsers = createFetchUsersTask(this);

  render() {
    return this.fetchUsers.render({
      pending: () => html`<p>Fetching users...</p>`,
      error: (e) => html`<p>An error occurred while fetching users</p>`,
      complete: (data) => html`
        <ul>
          ${data.map(
            (user) => html`
              <li>
                <img src=${user.picture.thumbnail} alt="user" />
                <p>${user.name.first} ${user.name.last}</p>
              </li>
            `
          )}
        </ul>
      `,
    });
  }
}

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