Advanced Tutorial of Vue-Vite-Typescript


Advanced Tutorial of Vue-Vite-Typescript

The following are the notes I took when I studied vue with reference to the official tutorial. The biggest difference between my notes and official tutorial is that I use typescript while the tutorial uses javascript. I suggest you learn vue following the official tutorial , but I firmly believe that you need to know some of the differences in the use of ts and js.

And please forgive my stiff English, I was just too lazy to switch input methods.

Component

The default root component is src/App.vue. The custom components should be placed in src/components.

All components would be mounted in src/main.ts.

Next you will learn the process of defining and using custom components

Define and use custom components

First, we will create a new file in src/components. The content should look like this.

<template>
  {{ msg }}
</template>

<script lang="ts">
import { defineComponent } from "vue";
export default defineComponent({
  name: "HelloWorld",
  data() {
    return {
      msg: "hello",
    };
  },
});
</script>

<style lang="less" scoped></style>

Now we have defined a component named HelloWorld.

Next, we need to import it in src/main.ts.

import { createApp } from "vue";
import HelloWorld from "./components/HelloWorld.vue";
// import HelloWorld
// `HelloWorld` is not necessary to be the name of the component

Then, you can declare a mount point in index.html.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <link rel="icon" href="/favicon.ico" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Vite App</title>
  </head>
  <body>
    <!-- the mount point is declared here -->
    <div id="test"></div>
    <script type="module" src="/src/main.ts"></script>
  </body>
</html>

Finally, you need to mount the component to the mount point. Continue to write in src/main.ts.

createApp(HelloWorld).mount("#test");

The components can also be defined and used in a simple way. For example, the code may look like this.

const app = Vue.createApp({})
app.component('button-counter', {
  data() {
    return {
      count: 0
    }
  },
  template: `
    <button @click="count++">
      You clicked me {{ count }} times.
    </button>`t
})

And you can simply reuse the components by add labels like this.

<div id="components-demo">
  <button-counter></button-counter>
</div>

The div with id components-demo contains a pair of labels with a name which is the same as the component.

Component registration

Components registered like this can be used globally. That means all components, including root component and child components can use these components.

const app = Vue.createApp({});

app.component("component-a", {
  /* ... */
});
app.component("component-b", {
  /* ... */
});
app.component("component-c", {
  /* ... */
});

app.mount("#app");
<div id="app">
  <component-a></component-a>
  <component-b></component-b>
  <component-c></component-c>
</div>

Components registered like this can only be used locally. That means only the root component can use these components.

import ComponentA from "./ComponentA.vue";
import ComponentB from "./ComponentB.vue";
const app = Vue.createApp({
  components: {
    "component-a": ComponentA,
    "component-b": ComponentB,
  },
});

The code below is the same.

import ComponentA from "./ComponentA.vue";
import ComponentB from "./ComponentB.vue";
const app = Vue.createApp({});
app.component("component-a", ComponentA);
app.component("component-b", ComponentB);

If you want to use ComponentA in ComponentB. You need to do like this.

ComponentB.component("component-a", ComponentA);

Interact with child components

Passing data to child components

In order to pass data to child components, we need to modify src/components/HelloWorld.vue like this.

<template>
  {{ msg }}
</template>

<script lang="ts">
import { defineComponent } from "vue";
export default defineComponent({
  name: "HelloWorld",
  props: ["msg"],
});
</script>

<style lang="less" scoped></style>

In the above code, we use props instead of data. Any value passed to a prop attribute will become a property on that component instance. And after a property is registered, we can pass data to it as a custom html attribute like this.

<div id="test">
  <HelloWorld msg="hello world"></HelloWorld>
</div>

Now, you can launch the project and watch the result in a broswer. But soon, you will find there is nothing displaying on the broswer. The reason is that our component has an uppercase name. We difined an uppercase name in our project but something changed it to a lowercase name when it finally arrived at broswer. So use a lowercase name is enough to fix the error.

Now, our code looks like this.

<template>
  {{ msg }}
</template>

<script lang="ts">
import { defineComponent } from "vue";
export default defineComponent({
  name: "hello-world",
  props: ["msg"],
});
</script>

<style lang="less" scoped></style>
<div id="test">
  <hello-world msg="hello world"></hello-world>
</div>
import { createApp } from "vue";
import HelloWorld from "./components/HelloWorld.vue";

const app = createApp({});
app.component("hello-world", HelloWorld);
app.mount("#test");

Then we can try a more complicated demo.

import { createApp } from "vue";
const App = {
  data() {
    return {
      posts: [
        { id: 1, title: "My journey with Vue" },
        { id: 2, title: "Blogging with Vue" },
        { id: 3, title: "Why Vue is so fun" },
      ],
    };
  },
};

const app = createApp(App);

app.component("blog-post", {
  props: ["title"],
  template: `<h4>{{ title }}</h4>`,
});

app.mount("#blog-posts-demo");
<div id="blog-posts-demo">
  <blog-post
    v-for="post in posts"
    :key="post.id"
    :title="post.title"
  ></blog-post>
</div>

There is still something which you need to notice. For an instance, see the code below.

<!-- src/components/Demo.vue -->
<template>
  {{ msg }}
</template>

<script lang="ts">
import { defineComponent } from "vue";

export default defineComponent({
  name: "demo",
  props: ["msg"],
});
</script>
/* src/main.ts */
import { createApp } from "vue";
import App from "./App.vue";
import EnlargeText from "./components/EnlargeText.vue";

const app = createApp(App);
app.component("enlarge-text", EnlargeText);
app.mount("#app");
<!-- src/App.vue -->
<template>
  <div>hello</div>
</template>

<script lang="ts">
import { defineComponent } from "vue";

export default defineComponent({
  name: "App",
});
</script>

<style lang="less"></style>
<!-- index.html -->
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>Vite App</title>
  </head>
  <body>
    <div id="app">
      <demo msg="world"></demo>
    </div>
    <script type="module" src="/src/main.ts"></script>
  </body>
</html>

In this example, we define templates in both main component and child component. And we try to display them in index.html together. But something would happen to the template of the child component. It is covered by the template of the main component. Take care of this problem. And if you really want to show them together, you can move <demo msg="world"></demo> from index.html to main component’s template.

Listening to the events of child components

Let’s ceate a new file named Demo.vue in src/components.

First, we modify src/components/Demo.vue like this.

<template>
  <div>
    <h4>
      {{ title }}
    </h4>
    <button @click="$emit('enlargeText')">Enlarge text</button>
  </div>
</template>

<script lang="ts">
import { defineComponent } from "vue";

export default defineComponent({
  name: "demo",
  props: ["title"],
  emits: ["enlargeText"],
});
</script>

In this file, we define an event of child component called enlargeText with emits. And we bind this to the button click event. Once the button is clicked, the super component will receive this event.

Then, we modify src/App.vue like this.

<template>
  <div>
    <demo
      :style="{ fontSize: postFontSize + 'em' }"
      @enlarge-text="postFontSize += 0.1"
      title="hello"
    ></demo>
  </div>
</template>

<script lang="ts">
import { defineComponent } from "vue";
import Demo from "./components/Demo.vue";

export default defineComponent({
  data() {
    return {
      postFontSize: 1,
    };
  },
  components: { Demo },
});
</script>

In this file, we define the mount point of the child component Demo. And we set its style with a variable postFontSize. Also, we define the response function for enlarge-text event. And finally, we import Demo from Demo.vue and register it as a clild component.

Be careful that enlarge-text is different from the event we defined in the child component called enlargeText. Although, enlargeText is also worked here, the broswer will interpret any uppercase characters as lowercase. So you’d better use enlarge-text.

Since we have imported the child component in src/App.vue, the src/main.ts becomes more simple.

import { createApp } from "vue";
import App from "./App.vue";

const app = createApp(App);
app.mount("#app");

Now you can run your project and check the result in your broswer.

If you are careful enough, you would find that emits is similar to props. props passes data to super component and emits passes event to super component.

Emit a value with an event

To go futher, I will introduce you how to emit a value with an event.

The code would look like this.

<button @click="$emit('enlargeText', 0.1)">
  Enlarge text
</button>

Then you can get the value with $event.

<demo
  :style="{ fontSize: postFontSize + 'em' }"
  @enlarge-text="postFontSize += $event"
  title="hello"
></demo>

And if the event handler is a method, the value will be passed as the first parameter.

<demo
  :style="{ fontSize: postFontSize + 'em' }"
  @enlarge-text="onEnlargeText"
  title="hello"
></demo>
<script lang="ts">
import { defineComponent } from "vue";
import Demo from "./components/Demo.vue";

export default defineComponent({
  data() {
    return {
      postFontSize: 1,
    };
  },
  components: { Demo },
  methods: {
    onEnlargeText(enlargeText: any) {
      this.postFontSize += enlargeText;
    },
  },
});
</script>
Use v-model on components

src/App.vue

<template>
  <div>
    <demo v-model="searchText"></demo>
    <!-- it's the same as the code below -->
    <!-- <demo -->
    <!-- :model-value="searchText" -->
    <!-- @update:model-value="searchText = $event" -->
    <!-- ></demo> -->
  </div>
</template>

<script lang="ts">
import { defineComponent } from "vue";
import Demo from "./components/Demo.vue";

export default defineComponent({
  components: { Demo },
});
</script>

src/components/Demo.vue

<template>
  <div>
    <input
      :value="modelValue"
      @input="$emit('update:modelValue', $event.target.value)"
    />
  </div>
</template>

<script lang="ts">
import { defineComponent } from "vue";

export default defineComponent({
  name: "demo",
  props: ["modelValue"],
  emits: ["update:modelValue"],
});
</script>

With the code above, we have implemented a simple input function. We use <demo v-model="searchText"></demo> to simply our code in this example. The key point is you need to bind some properties in child components before using v-model.

There is another way to define child components.

<template>
  <div>
    <input v-model="value" />
  </div>
</template>

<script lang="ts">
import { defineComponent } from "vue";

export default defineComponent({
  name: "demo",
  props: ["modelValue"],
  emits: ["update:modelValue"],
  computed: {
    value: {
      get(): any {
        return this.modelValue;
      },
      set(value: any) {
        this.$emit("update:modelValue", value);
      },
    },
  },
});
</script>

Content Distribution with slots

The name of the feature may be confusing, but the work is quite simple.

This feature means pass html content to a component. We have used this feature before.

app.component('alert-box', { template: `
<div class="demo-alert-box">
      <strong>Error!</strong>
      <slot></slot>
    </div>
` })

Dynamic components

It’s a feature to change components dynamicly when you swith to different tabs or other similar things, so that you can see different content.

The code is also simple. <component :is="currentTabComponent"></component> is all you need. What you need to do is changing currentTabComponent when needed.

DOM template parsing caveats

Some HTML elements, such as <ul>, <ol>, <table> and <select> have restrictions on what elements can appear inside them, and some elements such as <li>, <tr>, and <option> can only appear inside certain other elements.

For example:

<table>
  <demo></demo>
</table>

The custom component <demo> cannot be inside a pair of <table> label. To fix the error, you can use v-is with a allowed label instead.

<table>
  <tr v-is="'demo'"></tr>
</table>

Also, HTML attribute names are case-insensitive, so browsers will interpret any uppercase characters as lowercase. That means when you’re using in-DOM templates, camelCased prop names and event handler parameters need to use their kebab-cased (hyphen-delimited) equivalents. This has been mentioned before.

It should be noted that these limitations do not apply if you are using string templates from one of the following sources:

  • String templates (e.g. template: '...')
  • Single-file (.vue) components
  • <script type="text/x-template">

Summary

The most basic part of vue ends here, you are already be able to build some simple vue applications with this knowladge. To go futher, you can continue to learn more syntactic sugar following the official tutorial. It won’t be difficult for you.


文章作者: niuiic
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