Lit vs Vue 2 - JavaScript 框架语法对比

响应式

声明状态

Lit

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

@customElement("x-name")
export class XName extends LitElement {
  @state()
  name = "张三";

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

Vue 2

<script>
export default {
  data() {
    return {
      name: "张三",
    };
  },
};
</script>

<template>
  <h1>你好 {{ name }}</h1>
</template>

更新状态

Lit

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

@customElement("x-name")
export class XName extends LitElement {
  @state()
  name = "张三";

  constructor() {
    super();
    this.name = "李四";
  }

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

Vue 2

<script>
export default {
  data() {
    return {
      name: "张三",
    };
  },
  created() {
    this.name = "李四";
  },
};
</script>

<template>
  <h1>你好 {{ name }}</h1>
</template>

计算属性

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>`;
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      count: 10,
    };
  },
  computed: {
    doubleCount() {
      return this.count * 2;
    },
  },
};
</script>

<template>
  <div>{{ doubleCount }}</div>
</template>

模板语法

最简模板

Lit

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

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

Vue 2

<template>
  <h1>你好，世界</h1>
</template>

样式

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">我是红色的</h1>
      <button style=${styleMap({ fontSize: "10rem" })}>我是一个按钮</button>
    `;
  }
}

Vue 2

<template>
  <div>
    <h1 class="title">我是红色的</h1>
    <button style="font-size: 10rem">我是一个按钮</button>
  </div>
</template>

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

DOM循环

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 = ["红", "绿", "蓝"];

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

Vue 2

<script>
export default {
  data() {
    return {
      colors: ["红", "绿", "蓝"],
    };
  },
};
</script>

<template>
  <ul>
    <li v-for="color in colors" :key="color">
      {{ color }}
    </li>
  </ul>
</template>

点击事件

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>计数器: ${this.count}</p>
      <button @click=${this.incrementCount}>+1</button>
    `;
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      count: 0,
    };
  },
  methods: {
    incrementCount() {
      this.count++;
    },
  },
};
</script>

<template>
  <div>
    <p>计数器: {{ count }}</p>
    <button @click="incrementCount">+1</button>
  </div>
</template>

DOM引用

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" />`;
  }
}

Vue 2

<script>
export default {
  mounted() {
    this.$refs.inputElement.focus();
  },
};
</script>

<template>
  <input ref="inputElement" />
</template>

条件渲染

Lit

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

const TRAFFIC_LIGHTS = ["红灯", "黄灯", "绿灯"];

@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}>下一个灯</button>
      <p>现在亮着的是: ${this.light}</p>
      <p>
        你应该
        ${choose(this.light, [
          ["红灯", () => html`<span>停下</span>`],
          ["黄灯", () => html`<span>慢行</span>`],
          ["绿灯", () => html`<span>赶紧走</span>`],
        ])}
      </p>
    `;
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      TRAFFIC_LIGHTS: ["红灯", "黄灯", "绿灯"],
      lightIndex: 0,
    };
  },
  computed: {
    light() {
      return this.TRAFFIC_LIGHTS[this.lightIndex];
    },
  },
  methods: {
    nextLight() {
      this.lightIndex = (this.lightIndex + 1) % this.TRAFFIC_LIGHTS.length;
    },
  },
};
</script>

<template>
  <div>
    <button @click="nextLight">下一个灯</button>
    <p>现在亮着的是: {{ light }}</p>
    <p>
      你应该
      <span v-if="light === '红灯'">停下</span>
      <span v-else-if="light === '黄灯'">慢行</span>
      <span v-else-if="light === '绿灯'">赶紧走</span>
    </p>
  </div>
</template>

生命周期

组件加载时

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>页面标题: ${this.pageTitle}</p>`;
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      pageTitle: "",
    };
  },
  mounted() {
    this.pageTitle = document.title;
  },
};
</script>

<template>
  <p>页面标题: {{ pageTitle }}</p>
</template>

组件卸载时

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>当前时间: ${this.time}</p>`;
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      time: new Date().toLocaleTimeString(),
      timer: null,
    };
  },
  mounted() {
    this.timer = setInterval(() => {
      this.time = new Date().toLocaleTimeString();
    }, 1000);
  },
  beforeDestroy() {
    clearInterval(this.timer);
  },
};
</script>

<template>
  <p>当前时间: {{ time }}</p>
</template>

组件组合

组件Props传参

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="张三"
      age="20"
      .favouriteColors=${["green", "blue", "red"]}
      isAvailable
    ></user-profile>`;
  }
}

Vue 2

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

export default {
  components: {
    UserProfile,
  },
};
</script>

<template>
  <UserProfile
    name="张三"
    :age="20"
    :favorite-colors="['green', 'blue', 'red']"
    is-available
  />
</template>

向父组件emit事件

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>你快乐吗?</p>
      <answer-button
        @yes=${this.onAnswerYes}
        @no=${this.onAnswerNo}
      ></answer-button>
      <p style="font-size: 50px;">${this.isHappy ? "😀" : "😥"}</p>
    `;
  }
}

Vue 2

<script>
import AnswerButton from "./AnswerButton.vue";
export default {
  components: {
    AnswerButton,
  },
  data() {
    return {
      isHappy: true,
    };
  },
  methods: {
    onAnswerNo() {
      this.isHappy = false;
    },
    onAnswerYes() {
      this.isHappy = true;
    },
  },
};
</script>

<template>
  <div>
    <p>你快乐吗?</p>
    <AnswerButton @yes="onAnswerYes" @no="onAnswerNo" />
    <p style="font-size: 50px">
      {{ isHappy ? "😀" : "😥" }}
    </p>
  </div>
</template>

slot插槽

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>点我!</funny-button>`;
  }
}

Vue 2

<script>
import FunnyButton from "./FunnyButton.vue";
export default {
  components: {
    FunnyButton,
  },
};
</script>

<template>
  <FunnyButton> 点我! </FunnyButton>
</template>

slot插槽内容

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>这是传到slot的内容!</funny-button>
    `;
  }
}

Vue 2

<script>
import FunnyButton from "./FunnyButton.vue";
export default {
  components: {
    FunnyButton,
  },
};
</script>

<template>
  <div>
    <FunnyButton />
    <FunnyButton> 这是传到slot的内容! </FunnyButton>
  </div>
</template>

上下文

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: "abcdefg",
    email: "[email protected]",
  };

  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>欢迎回来, ${this.user.username}</h1>
      <user-profile
        .user="${this.user}"
        .updateUsername=${this.updateUsername.bind(this)}
      ></user-profile>`;
  }
}

Vue 2

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

export default {
  components: { UserProfile },
  provide() {
    return {
      user: Object.assign(this.user, {
        updateUsername: this.updateUsername,
      }),
    };
  },
  data() {
    return {
      user: {
        id: 1,
        username: "abcdefg",
        email: "[email protected]",
      },
    };
  },
  methods: {
    updateUsername(newUsername) {
      this.user.username = newUsername;
    },
  },
};
</script>

<template>
  <div>
    <h1>欢迎回来, {{ user.username }}</h1>
    <UserProfile />
  </div>
</template>

表单输入

输入框

Lit

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

@customElement("input-hello")
export class InputHello extends LitElement {
  @state()
  text = "你好世界";

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

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

Vue 2

<script>
export default {
  data() {
    return {
      text: "你好世界",
    };
  },
};
</script>

<template>
  <div>
    <p>{{ text }}</p>
    <input v-model="text" />
  </div>
</template>

复选框

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">这是一个checkbox</label>
    `;
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      isAvailable: true,
    };
  },
};
</script>

<template>
  <div>
    <input id="is-available" v-model="isAvailable" type="checkbox" />
    <label for="is-available">这是一个checkbox</label>
  </div>
</template>

单选框

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>你选择了: ${this.picked}</div>

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

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

Vue 2

<script>
export default {
  data() {
    return {
      picked: "red",
    };
  },
};
</script>

<template>
  <div>
    <div>你选择了: {{ picked }}</div>

    <input id="blue-pill" v-model="picked" type="radio" value="blue" />
    <label for="blue-pill">蓝色</label>

    <input id="red-pill" v-model="picked" type="radio" value="red" />
    <label for="red-pill">红色</label>
  </div>
</template>

选择器

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: "红" },
    { id: 2, text: "蓝" },
    { id: 3, text: "绿" },
    { id: 4, text: "灰", 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>
    `;
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      selectedColorId: 2,
      colors: [
        { id: 1, text: "红" },
        { id: 2, text: "蓝" },
        { id: 3, text: "绿" },
        { id: 4, text: "灰", isDisabled: true },
      ],
    };
  },
};
</script>

<template>
  <select v-model="selectedColorId">
    <option
      v-for="color in colors"
      :key="color.id"
      :value="color.id"
      :disabled="color.isDisabled"
    >
      {{ color.text }}
    </option>
  </select>
</template>

Web应用特性

渲染应用

Lit

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

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

Vue 2

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

fetch获取数据

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>正在获取用户信息……</p>`,
      error: (e) => html`<p>获取用户信息出错</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>
      `,
    });
  }
}

Vue 2

<script>
export default {
  data() {
    return {
      isLoading: false,
      error: undefined,
      users: undefined,
    };
  },
  mounted() {
    this.fetchData();
  },
  methods: {
    async fetchData() {
      this.isLoading = true;
      try {
        const response = await fetch("https://randomuser.me/api/?results=3");
        const { results: users } = await response.json();
        this.users = users;
        this.error = undefined;
      } catch (error) {
        this.error = error;
      } finally {
        this.users = undefined;
        this.isLoading = false;
      }
    },
  },
};
</script>

<template>
  <p v-if="isLoading">正在获取用户信息……</p>
  <p v-else-if="error">获取用户信息出错</p>
  <ul v-else-if="users">
    <li v-for="user in users" :key="user.login.uuid">
      <img :src="user.picture.thumbnail" alt="user" />
      <p>
        {{ user.name.first }}
        {{ user.name.last }}
      </p>
    </li>
  </ul>
</template>

响应式 #

声明状态 #

Lit

Vue 2

更新状态 #

Lit

Vue 2

计算属性 #

Lit

Vue 2

模板语法 #

最简模板 #

Lit

Vue 2

样式 #

Lit

Vue 2

DOM循环 #

Lit

Vue 2

点击事件 #

Lit

Vue 2

DOM引用 #

Lit

Vue 2

条件渲染 #

Lit

Vue 2

生命周期 #

组件加载时 #

Lit

Vue 2

组件卸载时 #

Lit

Vue 2

组件组合 #

组件Props传参 #

Lit

Vue 2

向父组件emit事件 #

Lit

Vue 2

slot插槽 #

Lit

Vue 2

slot插槽内容 #

Lit

Vue 2

上下文 #

Lit

Vue 2

表单输入 #

输入框 #

Lit

Vue 2

复选框 #

Lit

Vue 2

单选框 #

Lit

Vue 2

选择器 #

Lit

Vue 2

Web应用特性 #

渲染应用 #

Lit

Vue 2

fetch获取数据 #

Lit

Vue 2

响应式

声明状态

更新状态

计算属性

模板语法

最简模板

样式

DOM循环

点击事件

DOM引用

条件渲染

生命周期

组件加载时

组件卸载时

组件组合

组件Props传参

向父组件emit事件

slot插槽

slot插槽内容

上下文

表单输入

输入框

复选框

单选框

选择器

Web应用特性

渲染应用

fetch获取数据