响应式
声明状态
更新状态
计算属性
<script>
let count = $state(10);
const doubleCount = $derived(count * 2);
</script>
<div>{doubleCount}</div>
模板语法
最简模板
样式
<h1 class="title">我是红色的</h1>
<button style="font-size: 10rem;">我是一个按钮</button>
<style>
.title {
color: red;
}
</style>
DOM循环
点击事件
<script>
let count = $state(0);
function incrementCount() {
count++;
}
</script>
<p>计数器: {count}</p>
<button onclick={incrementCount}>+1</button>
DOM引用
条件渲染
<script>
const TRAFFIC_LIGHTS = ["红灯", "黄灯", "绿灯"];
let lightIndex = $state(0);
const light = $derived(TRAFFIC_LIGHTS[lightIndex]);
function nextLight() {
lightIndex = (lightIndex + 1) % TRAFFIC_LIGHTS.length;
}
</script>
<button onclick={nextLight}>下一个灯</button>
<p>现在亮着的是: {light}</p>
<p>
你应该
{#if light === "红灯"}
<span>停下</span>
{:else if light === "黄灯"}
<span>慢行</span>
{:else if light === "绿灯"}
<span>赶紧走</span>
{/if}
</p>
import { track } from "ripple";
const TRAFFIC_LIGHTS = ["红灯", "黄灯", "绿灯"];
export default function TrafficLight() {
let &[lightIndex] = track(0);
let &[light] = track(() => TRAFFIC_LIGHTS[lightIndex]);
function nextLight() {
lightIndex = (lightIndex + 1) % TRAFFIC_LIGHTS.length;
}
return <>
<button onClick={nextLight}>"下一个灯"</button>
<p>"现在亮着的是: "{light}</p>
<p>
"你应该 "
if (light === "红灯") {
<span>"停下"</span>
} else if (light === "黄灯") {
<span>"慢行"</span>
} else if (light === "绿灯") {
<span>"赶紧走"</span>
}
</p>
</>;
}
生命周期
组件加载时
<script>
let pageTitle = $state("");
$effect(() => {
pageTitle = document.title;
});
</script>
<p>页面标题: {pageTitle}</p>
组件卸载时
<script>
let time = $state(new Date().toLocaleTimeString());
$effect(() => {
const timer = setInterval(() => {
time = new Date().toLocaleTimeString();
}, 1000);
return () => clearInterval(timer);
});
</script>
<p>当前时间: {time}</p>
import { effect, track } from "ripple";
export default function Time() {
let &[time] = track(new Date().toLocaleTimeString());
effect(() => {
const timer = setInterval(() => {
time = new Date().toLocaleTimeString();
}, 1000);
return () => clearInterval(timer);
});
return <h1>"当前时间: "{time}</h1>;
}
组件组合
组件Props传参
<script>
import UserProfile from "./UserProfile.svelte";
</script>
<UserProfile
name="张三"
age={20}
favouriteColors={["green", "blue", "red"]}
isAvailable
/>
向父组件emit事件
<script>
import AnswerButton from "./AnswerButton.svelte";
let isHappy = $state(true);
function onAnswerNo() {
isHappy = false;
}
function onAnswerYes() {
isHappy = true;
}
</script>
<p>你快乐吗?</p>
<AnswerButton onYes={onAnswerYes} onNo={onAnswerNo} />
<p style="font-size: 50px;">{isHappy ? "😀" : "😥"}</p>
import { track } from "ripple";
import { AnswerButton } from "./AnswerButton.tsrx";
export function App() {
let &[isHappy] = track(true);
function onAnswerNo() {
isHappy = false;
}
function onAnswerYes() {
isHappy = true;
}
return <>
<p>"你快乐吗?"</p>
<AnswerButton onYes={onAnswerYes} onNo={onAnswerNo} />
<p style={{ fontSize: "50px" }}>{isHappy ? "😀" : "😥"}</p>
</>;
}
slot插槽
slot插槽内容
上下文
<script>
import { setContext } from "svelte";
import UserProfile from "./UserProfile.svelte";
import createUserState from "./createUserState.svelte.js";
const user = createUserState({
id: 1,
username: "abcdefg",
email: "[email protected]",
});
setContext("user", user);
</script>
<h1>欢迎回来, {user.username}</h1>
<UserProfile />
import { RippleObject } from "ripple";
import { UserContext } from "./UserContext.tsrx";
import { UserProfile } from "./UserProfile.tsrx";
export function App() {
const user = new RippleObject({
id: 1,
username: "abcdefg",
email: "[email protected]",
});
UserContext.set(user);
return <>
<h1>"欢迎回来, "{user.username}</h1>
<UserProfile />
</>;
}
表单输入
输入框
复选框
<script>
let isAvailable = $state(false);
</script>
<input id="is-available" type="checkbox" bind:checked={isAvailable} />
<label for="is-available">这是一个checkbox</label>
单选框
<script>
let picked = $state("red");
</script>
<div>你选择了: {picked}</div>
<input id="blue-pill" bind:group={picked} type="radio" value="blue" />
<label for="blue-pill">蓝色</label>
<input id="red-pill" bind:group={picked} type="radio" value="red" />
<label for="red-pill">红色</label>
import { bindGroup, track } from "ripple";
export default function PickPill() {
let &[picked, pickedTracked] = track("red");
return <>
<div>"你选择了: "{picked}</div>
<input
id="blue-pill"
type="radio"
value="blue"
ref={bindGroup(pickedTracked)}
/>
<label for="blue-pill">"蓝色"</label>
<input
id="red-pill"
type="radio"
value="red"
ref={bindGroup(pickedTracked)}
/>
<label for="red-pill">"红色"</label>
</>;
}
选择器
<script>
let selectedColorId = $state(2);
const colors = [
{ id: 1, text: "红" },
{ id: 2, text: "蓝" },
{ id: 3, text: "绿" },
{ id: 4, text: "灰", isDisabled: true },
];
</script>
<select bind:value={selectedColorId}>
{#each colors as color}
<option value={color.id} disabled={color.isDisabled}>
{color.text}
</option>
{/each}
</select>
import { bindValue, track } from "ripple";
const colors = [
{ id: 1, text: "红" },
{ id: 2, text: "蓝" },
{ id: 3, text: "绿" },
{ id: 4, text: "灰", isDisabled: true },
];
export default function ColorSelect() {
let &[selectedColorId, selectedColorIdTracked] = track(2);
return <select ref={bindValue(selectedColorIdTracked)}>
for (const color of colors; key color.id) {
<option value={color.id} disabled={color.isDisabled}>
{color.text}
</option>
}
</select>;
}
Web应用特性
渲染应用
Svelte 5
<!doctype html>
<html>
<body>
<div id="app"></div>
<script type="module" src="./app.js"></script>
</body>
</html>
Ripple
<!doctype html>
<html>
<body>
<div id="app"></div>
<script type="module" src="./main.js"></script>
</body>
</html>
fetch获取数据
<script>
import useFetchUsers from "./useFetchUsers.svelte.js";
const response = useFetchUsers();
</script>
{#if response.isLoading}
<p>正在获取用户信息……</p>
{:else if response.error}
<p>获取用户信息出错</p>
{:else if response.users}
<ul>
{#each response.users as user}
<li>
<img src={user.picture.thumbnail} alt="user" />
<p>
{user.name.first}
{user.name.last}
</p>
</li>
{/each}
</ul>
{/if}
import { useFetchUsers } from "./useFetchUsers.tsrx";
export function App() {
const data = useFetchUsers();
return <>
if (data.isLoading) {
<p>"正在获取用户信息……"</p>
} else if (data.error) {
<p>"获取用户信息出错"</p>
} else if (data.users) {
<ul>
for (const user of data.users; key user.login.uuid) {
<li>
<img src={user.picture.thumbnail} alt="用户" />
<p>{user.name.first}" "{user.name.last}</p>
</li>
}
</ul>
}
</>;
}