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Merge pull request #10 from typescript-cheatsheets/chiubaca-brain-dump
Docs Reshuffle & Mini Brain Dump
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‎README.md‎

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Cheatsheets for experienced Vue developers getting started with TypeScript.
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- [Vue 3 specifics](vue-3.md)
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- [Class Components & Decorators](class-components.md)
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# Section 1: Setup
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});
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```
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### Class Components
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[Vue Class Components](https://class-component.vuejs.org/) offers an alternative class-style syntax for Vue components which integrates well with TypeScript.
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To have consistent support for decorators in your Vue components, it's also recommended to install [vue-property-decorator](https://github.com/kaorun343/vue-property-decorator).
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To get started with both libraries in your existing Vue project, run:
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```
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npm install vue-class-component vue-property-decorator
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```
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You only need to import `vue-property-decorator` into your `.vue` file as it extends `vue-class-component`.
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You can now write TS in your components like this:
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```vue
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<template>
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<div>
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{{ count }}
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<button v-on:click="increment">+</button>
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<button v-on:click="decrement">-</button>
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{{ computedValue }}
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</div>
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</template>
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<script lang="ts">
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import { Vue, Component } from "vue-property-decorator";
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@Component
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export default class Hello extends Vue {
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count: number = 0
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vue: string = "vue"
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ts: string = "ts"
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// Lifecycle methods can be accessed like this
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mounted() {
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console.log('component mounted')
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}
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// Method are component methods
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increment(): void {
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this.count++
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}
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decrement(): void {
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this.count--
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}
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// Computed values are getters
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get computedValue(): string {
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return `${vue} and ${ts} rocks!`
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}
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}
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</script>
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```
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See the [full guide for Vue Class Components](https://class-component.vuejs.org/guide/class-component.html#data).
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> _Class components should not confused with the now abandoned [Class API proposal](https://github.com/vuejs/rfcs/pull/17#issuecomment-494242121)._
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## Props
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`PropType` can be used to annotate props with a particular object shape.
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</script>
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```
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With vue-class-components and vue-property-decorator, you can use the `Prop` decorator:
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Alternatively, you can also annote your prop types with an anonymous function:
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```vue
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import Vue from 'vue'
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<script lang="ts">
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import { Vue, Component, Prop } from "vue-property-decorator";
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import Vue from "vue";
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interface PersonInfo {
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firstName: string,
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surname: string,
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age: number
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}
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@Component
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export default class InfoCard extends Vue {
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@Prop({ required: true }) readonly info: PersonInfo;
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}
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export default Vue.extend({
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name: "InfoCard",
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props: {
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info: {
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type: Object as () => PersonInfo,
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required: true
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}
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}
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});
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</script>
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```
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## Data Properties
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## Data Properties (Options API)
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You can enforce types on Vue data properties by annotating the return data object:
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```
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Note that [type assertion](https://www.typescriptlang.org/docs/handbook/basic-types.html#type-assertions) like this does not provide any type safety. If for example, the `contents` property was missing in `newPost`, TypeScript would not catch this error.
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## Computed Properties (Options API)
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Typing the return type for your computed properties is important especially when `this` is involved as TypeScript sometimes has trouble infering the type.
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```ts
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export default Vue.extend({
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data() {
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return {
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name: 'World',
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}
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},
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computed: {
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greet(): string { //👈 Remember to annotate your computed properties like so.
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return 'Hello ' + this.name
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},
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}
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})
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```
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>
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# Other Vue + TypeScript resources
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- Views on Vue podcast - https://devchat.tv/views-on-vue/vov-076-typescript-tell-all-with-jack-koppa/
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- Focuses a lot on class components and vue-property-decorator - https://blog.logrocket.com/how-to-write-a-vue-js-app-completely-in-typescript/
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- Vue 3 Hooks and Type Safety with TypeScript - https://www.youtube.com/watch?v=aJdi-uEKYAc

‎class-components.md‎

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# Class Components
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## Overview
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[Vue Class Components](https://class-component.vuejs.org/) offers an alternative class-style syntax for Vue components which integrates well with TypeScript.
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To have consistent support for decorators in your Vue components, it's also recommended to install [vue-property-decorator](https://github.com/kaorun343/vue-property-decorator).
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To get started with both libraries in your existing Vue project, run:
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```
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npm install vue-class-component vue-property-decorator
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```
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You only need to import `vue-property-decorator` into your `.vue` file as it extends `vue-class-component`.
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You can now write TS in your components like this:
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```vue
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<template>
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<div>
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{{ count }}
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<button v-on:click="increment">+</button>
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<button v-on:click="decrement">-</button>
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{{ computedValue }}
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</div>
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</template>
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<script lang="ts">
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import { Vue, Component } from "vue-property-decorator";
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@Component
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export default class Hello extends Vue {
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count: number = 0
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vue: string = "vue"
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ts: string = "ts"
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// Lifecycle methods can be accessed like this
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mounted() {
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console.log('component mounted')
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}
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// Method are component methods
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increment(): void {
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this.count++
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}
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decrement(): void {
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this.count--
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}
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// Computed values are getters
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get computedValue(): string {
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return `${vue} and ${ts} rocks!`
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}
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}
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</script>
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```
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See the [full guide for Vue Class Components](https://class-component.vuejs.org/guide/class-component.html#data).
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> _Class components should not confused with the now abandoned [Class API proposal](https://github.com/vuejs/rfcs/pull/17#issuecomment-494242121)._
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## Props
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You can use the `Prop` decorator to annoate your prop types like so:
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```ts
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<script lang="ts">
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import { Vue, Component, Prop } from "vue-property-decorator";
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interface PersonInfo {
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firstName: string,
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surname: string,
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age: number
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}
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@Component
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export default class InfoCard extends Vue {
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@Prop() readonly info!: PersonInfo;
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@Prop({ default: false }) readonly admin?: boolean;
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}
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</script>
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```
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Is equivalent to:
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```ts
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import Vue from "vue-property-decorator";
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import Vue, { PropType } from 'vue'
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interface PersonInfo {
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firstName: string,
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surname: string,
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age: number
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}
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export default {
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props: {
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info: {
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type: Object as PropType<PersonInfo>,
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required: true
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},
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admin: {
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type: Boolean,
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default: false
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}
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},
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}
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```

‎vue-3.md‎

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export const welcome = computed(() => `Welcome, ${props.name}!`)
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```
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## Composition API
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### Refs
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Vue can infer the type of your `ref`'s but if you need to represent some more complex types you can do so with generics:
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```ts
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import {ref} from "vue"
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interface PersonInfo {
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firstName: string,
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surname: string,
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age: number
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}
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const people = ref<PersonInfo[]>([])
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```
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Alternatively you can use casting with `as`. This should be used if the type is unknown. Consider this example where we create a composition wrapper function around `fetch` and we dont know the data structure that will be returned.
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```ts
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import { ref, Ref } from "vue";
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type ApiRequest = () => Promise<void>;
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// When using this function we can supply the type via generics
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export function useAPI<T>(url: RequestInfo, options?: RequestInit) {
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const response = ref() as Ref<T>; // 👈 note we're typing our ref using `as`
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const request: ApiRequest = async () => {
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const resp = await fetch(url, options);
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const data = await resp.json();
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response.value = data;
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};
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return { response, request };
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}
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```

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