Reactivity

Declare state

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<h1>Hello {{this.name}}</h1>

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import { component$, useSignal } from "@builder.io/qwik";

export const Name = component$(() => {
  const name = useSignal("John");

  return <h1>Hello {name.value}</h1>;
});

Update state

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<h1>Hello {{this.name}}</h1>

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import { component$, useTask$, useSignal } from "@builder.io/qwik";

export const Name = component$(() => {
  const name = useSignal("John");

  useTask$(() => {
    name.value = "Jane";
  });

  return <h1>Hello {name.value}</h1>;
});

Computed state

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<div>{{this.doubleCount}}</div>

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import { component$, useSignal, useComputed$ } from "@builder.io/qwik";

export const DoubleCount = component$(() => {
  const count = useSignal(10);
  const doubleCount = useComputed$(() => count.value * 2);

  return <div>{doubleCount.value}</div>;
});

Templating

Minimal template

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<h1>Hello world</h1>

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export const HelloWorld = () => {
  return <div>Hello World</div>;
};

Styling

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/* using: https://github.com/salsify/ember-css-modules */
.title {
  color: red;
}

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import { component$, useStyles$ } from "@builder.io/qwik";

export const App = component$(() => {
  useStyles$(`
    .title {
      color: red;
    }
    `);

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

Loop

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<ul>
  {{#each (array "red" "green" "blue") as |color|}}
    <li>{{color}}</li>
  {{/each}}
</ul>

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import { component$ } from "@builder.io/qwik";

export const Colors = component$(() => {
  const colors = ["red", "green", "blue"];
  return (
    <ul>
      {colors.map((color) => (
        <li key={color}>{color}</li>
      ))}
    </ul>
  );
});

Event click

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<p>Counter: {{this.count}}</p>
<button {{on "click" this.incrementCount}}>+1</button>

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import { component$, useSignal, $ } from "@builder.io/qwik";

export const Counter = component$(() => {
  const count = useSignal(0);

  const incrementCount = $(() => {
    count.value++;
  });

  return (
    <>
      <p>Counter: {count.value}</p>
      <button onClick$={incrementCount}>Increment</button>
    </>
  );
});

Dom ref

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<input {{this.autofocus}} />

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import { component$, useVisibleTask$, useSignal } from "@builder.io/qwik";

export const InputFocused = component$(() => {
  const inputElement = useSignal<HTMLInputElement>();

  useVisibleTask$(({ track }) => {
    const el = track(inputElement);
    el?.focus();
  });

  return <input type="text" ref={inputElement} />;
});

Conditional

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

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import { $, component$, useComputed$, useSignal } from "@builder.io/qwik";

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

export const TrafficLight = component$(() => {
  const lightIndex = useSignal(0);

  const light = useComputed$(() => TRAFFIC_LIGHTS[lightIndex.value]);

  const nextLight = $(() => {
    lightIndex.value = (lightIndex.value + 1) % TRAFFIC_LIGHTS.length;
  });

  return (
    <>
      <button onClick$={nextLight}>Next light</button>
      <p>Light is: {light.value}</p>
      <p>
        You must {light.value === "red" && <span>STOP</span>}
        {light.value === "orange" && <span>SLOW DOWN</span>}
        {light.value === "green" && <span>GO</span>}
      </p>
    </>
  );
});

Lifecycle

On mount

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<p>Page title is: {{(this.pageTitle)}}</p>

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import { component$, useVisibleTask$, useStore } from "@builder.io/qwik";

export const App = component$(() => {
  const store = useStore({
    pageTitle: "",
  });

  useVisibleTask$(() => {
    store.pageTitle = document.title;
  });

  return <p>Page title: {store.pageTitle}</p>;
});

On unmount

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

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import { component$, useVisibleTask$, useStore } from "@builder.io/qwik";

export const App = component$(() => {
  const store = useStore({
    time: new Date().toLocaleTimeString(),
  });

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

    cleanup(() => clearInterval(timer));
  });

  return <p>Current time: {store.time}</p>;
});

Component composition

Props

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<UserProfile
  @name="John"
  @age={{20}}
  @favouriteColors={{array "green" "blue" "red"}}
  @isAvailable={{true}}
/>

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import { component$ } from "@builder.io/qwik";
import UserProfile from "./UserProfile";

const App = component$(() => {
  return (
    <UserProfile
      name="John"
      age={20}
      favouriteColors={["green", "blue", "red"]}
      isAvailable
    />
  );
});

export default App;

Emit to parent

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<p>Are you happy?</p>
<AnswerButton @onYes={{this.handleYes}} @onNo={{this.handleNo}} />
<p style="font-size: 50px;">{{if this.isHappy "😀" "😥"}}</p>

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import { $, component$, useStore } from "@builder.io/qwik";
import AnswerButton from "./AnswerButton";

const App = component$(() => {
  const store = useStore({
    isHappy: true,
  });

  const onAnswerNo = $(() => {
    store.isHappy = false;
  });

  const onAnswerYes = $(() => {
    store.isHappy = true;
  });

  return (
    <>
      <p>Are you happy?</p>
      <AnswerButton onYes$={onAnswerYes} onNo$={onAnswerNo} />
      <p style={{ fontSize: 50 }}>{store.isHappy ? "😀" : "😥"}</p>
    </>
  );
});

export default App;

Slot

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<FunnyButton> Click me! </FunnyButton>

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import FunnyButton from "./FunnyButton";

export default function App() {
  return <FunnyButton>Click me!</FunnyButton>;
}

Slot fallback

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

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import FunnyButton from "./FunnyButton";

export default function App() {
  return (
    <>
      <FunnyButton />
      <FunnyButton>Click me!</FunnyButton>
    </>
  );
}

Context

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<UserProfile />

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import {
  component$,
  useStore,
  useContextProvider,
  createContext,
  $,
} from "@builder.io/qwik";
import UserProfile from "./UserProfile";

export const UserContext = createContext("user-context");

const App = component$(() => {
  const user = useStore({
    id: 1,
    username: "unicorn42",
    email: "[email protected]",
  });

  const updateUsername = $((newUsername) => {
    user.username = newUsername;
  });

  useContextProvider(UserContext, { user, updateUsername });

  return (
    <>
      <h1>Welcome back, {user.username}</h1>
      <UserProfile />
    </>
  );
});

export default App;

Form input

Input text

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<p>{{this.text}}</p>
<input value={{this.text}} {{on "input" this.handleInput}} />

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import { component$, useSignal } from "@builder.io/qwik";

const InputHello = component$(() => {
  const text = useSignal("");

  return (
    <>
      <p>{text.value}</p>
      <input bind:value={text} />
    </>
  );
});

export default InputHello;

Checkbox

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<input
  id="is-available"
  type="checkbox"
  checked={{this.isAvailable}}
  {{on "change" this.handleChange}}
/>
<label for="is-available">Is available</label>

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import { component$, useSignal } from "@builder.io/qwik";

const IsAvailable = component$(() => {
  const isAvailable = useSignal(false);

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

export default IsAvailable;

Radio

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

<input
  id="blue-pill"
  type="radio"
  value="blue"
  checked={{eq this.picked "blue"}}
  {{on "change" this.handleChange}}
/>
<label htmlFor="blue-pill">Blue pill</label>

<input
  id="red-pill"
  type="radio"
  value="red"
  checked={{eq this.picked "red"}}
  {{on "change" this.handleChange}}
/>
<label htmlFor="red-pill">Red pill</label>

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import { component$, useSignal } from "@builder.io/qwik";

const PickPill = component$(() => {
  const pickedColor = useSignal("red");

  return (
    <>
      <div>Picked: {pickedColor.value}</div>
      <input
        id="blue-pill"
        type="radio"
        bind:value={pickedColor}
        checked={pickedColor.value === "blue"}
        value="blue"
      />
      <label for="blue-pill">Blue pill</label>

      <input
        id="red-pill"
        type="radio"
        checked={pickedColor.value === "red"}
        bind:value={pickedColor}
        value="red"
      />
      <label for="red-pill">Red pill</label>
    </>
  );
});

export default PickPill;

Select

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<select {{on "change" this.select}}>
  {{#each this.colors as |color|}}
    <option
      value={{color.id}}
      disabled={{color.isDisabled}}
      selected={{eq color.id this.selectedColorId}}
    >
      {{color.text}}
    </option>
  {{/each}}
</select>

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import { component$, useSignal } from "@builder.io/qwik";

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

const ColorSelect = component$(() => {
  const selectedColorId = useSignal("2");

  return (
    <select bind:value={selectedColorId}>
      {colors.map((color) => (
        <option
          key={color.id}
          value={color.id}
          disabled={color.isDisabled}
          selected={`${color.id}` === selectedColorId.value}
        >
          {color.text}
        </option>
      ))}
    </select>
  );
});

export default ColorSelect;

Webapp features

Render app

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Missing snippet Help us to improve Component Party logo

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<!doctype html>
<html>
  <body>
    <div id="app"></div>
    <script type="module" src="./main.tsx"></script>
  </body>
</html>

Fetch data

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{{#let (this.fetchUsers) as |request|}}
  {{#if request.isLoading}}

    <p>Fetching users...</p>

  {{else if request.error}}

    <p>An error occurred while fetching users</p>

  {{else}}

    <ul>
      {{#each request.users as |user|}}
        <li>
          <img src={{user.picture.thumbnail}} alt="user" />
          <p>{{user.name.first}} {{user.name.last}}</p>
        </li>
      {{/each}}
    </ul>

  {{/if}}
{{/let}}

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import { component$, useResource$, Resource } from "@builder.io/qwik";

type UsersResponse = {
  results: {
    picture: {
      thumbnail: string;
    };
    name: {
      first: string;
      last: string;
    };
  }[];
};

export async function fetchUsers() {
  return (await fetch("https://randomuser.me/api/?results=3")).json();
}

export const App = component$(() => {
  const data = useResource$<UsersResponse>(fetchUsers);

  return (
    <Resource
      value={data}
      onPending={() => <p>Fetching users...</p>}
      onRejected={() => <p>An error occurred while fetching users</p>}
      onResolved={({ results: users }) => (
        <ul>
          {users.map((user) => (
            <li>
              <img src={user.picture.thumbnail} alt="user" />
              <p>
                {user.name.first} {user.name.last}
              </p>
            </li>
          ))}
        </ul>
      )}
    />
  );
});