vue-property-decorator

What is vue-property-decorator?

The vue-property-decorator package provides TypeScript decorators for Vue components, making it easier to write Vue components with TypeScript. It simplifies the syntax and enhances code readability by allowing the use of decorators for properties, methods, and lifecycle hooks.

What are vue-property-decorator's main functionalities?

Component Decorator

The @Component decorator is used to define a Vue component. It allows you to use class-style syntax to define your component, making the code more organized and readable.

import { Vue, Component } from 'vue-property-decorator';

@Component
export default class MyComponent extends Vue {
  // Component logic here
}

Prop Decorator

The @Prop decorator is used to define props in a Vue component. It simplifies the syntax for declaring props and their types, making the code more concise.

import { Vue, Component, Prop } from 'vue-property-decorator';

@Component
export default class MyComponent extends Vue {
  @Prop(String) readonly myProp!: string;
}

Watch Decorator

The @Watch decorator is used to watch for changes in a component's data properties. It simplifies the syntax for setting up watchers, making the code more readable.

import { Vue, Component, Watch } from 'vue-property-decorator';

@Component
export default class MyComponent extends Vue {
  myData = '';

  @Watch('myData')
  onMyDataChanged(newVal: string, oldVal: string) {
    console.log(`myData changed from ${oldVal} to ${newVal}`);
  }
}

Emit Decorator

The @Emit decorator is used to emit custom events from a component. It simplifies the syntax for emitting events, making the code more concise and readable.

import { Vue, Component, Emit } from 'vue-property-decorator';

@Component
export default class MyComponent extends Vue {
  @Emit('myEvent')
  myMethod() {
    return 'data';
  }
}

Model Decorator

The @Model decorator is used to create a two-way binding for a prop. It simplifies the syntax for defining v-model bindings, making the code more concise.

import { Vue, Component, Model } from 'vue-property-decorator';

@Component
export default class MyComponent extends Vue {
  @Model('change', { type: String }) readonly value!: string;
}

Other packages similar to vue-property-decorator

vue-class-component

The vue-class-component package allows you to define Vue components using class-style syntax in TypeScript. It provides a base class for Vue components and supports decorators for properties and methods. Compared to vue-property-decorator, it is more lightweight but requires additional packages for full decorator support.

vuex-class

The vuex-class package provides TypeScript decorators and helpers for Vuex. It allows you to use class-style syntax to define Vuex modules, actions, getters, and mutations. While it focuses on Vuex integration, it complements vue-property-decorator by providing similar decorator-based syntax for Vuex.

README

Vue Property Decorator

This library fully depends on vue-class-component, so please read its README before using this library.

License

MIT License

Install

npm i -S vue-property-decorator

Usage

There are several decorators and 1 function (Mixin):

• @Prop
• @PropSync
• @Model
• @ModelSync
• @Watch
• @Provide
• @Inject
• @ProvideReactive
• @InjectReactive
• @Emit
• @Ref
• @VModel
• @Component (provided by vue-class-component)
• Mixins (the helper function named mixins provided by vue-class-component)

See also

vuex-class

@Prop(options: (PropOptions | Constructor[] | Constructor) = {}) decorator

import { Vue, Component, Prop } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @Prop(Number) readonly propA: number | undefined
  @Prop({ default: 'default value' }) readonly propB!: string
  @Prop([String, Boolean]) readonly propC: string | boolean | undefined
}

is equivalent to

export default {
  props: {
    propA: {
      type: Number,
    },
    propB: {
      default: 'default value',
    },
    propC: {
      type: [String, Boolean],
    },
  },
}

Note that:

If you'd like to set type property of each prop value from its type definition, you can use reflect-metadata.

1. Set emitDecoratorMetadata to true.
2. Import reflect-metadata before importing vue-property-decorator (importing reflect-metadata is needed just once.)

import 'reflect-metadata'
import { Vue, Component, Prop } from 'vue-property-decorator'

@Component
export default class MyComponent extends Vue {
  @Prop() age!: number
}

Each prop's default value need to be defined as same as the example code shown in above.

It's not supported to define each default property like @Prop() prop = 'default value' .

@PropSync(propName: string, options: (PropOptions | Constructor[] | Constructor) = {}) decorator

import { Vue, Component, PropSync } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @PropSync('name', { type: String }) syncedName!: string
}

is equivalent to

export default {
  props: {
    name: {
      type: String,
    },
  },
  computed: {
    syncedName: {
      get() {
        return this.name
      },
      set(value) {
        this.$emit('update:name', value)
      },
    },
  },
}

@PropSync works like @Prop besides the fact that it takes the propName as an argument of the decorator, and also creates a computed getter and setter behind the scenes. This way you can interface with the property as if it was a regular data property whilst making it as easy as appending the .sync modifier in the parent component.

@Model(event?: string, options: (PropOptions | Constructor[] | Constructor) = {}) decorator

import { Vue, Component, Model } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @Model('change', { type: Boolean }) readonly checked!: boolean
}

is equivalent to

export default {
  model: {
    prop: 'checked',
    event: 'change',
  },
  props: {
    checked: {
      type: Boolean,
    },
  },
}

@Model property can also set type property from its type definition via reflect-metadata .

@ModelSync(propName: string, event?: string, options: (PropOptions | Constructor[] | Constructor) = {}) decorator

import { Vue, Component, ModelSync } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @ModelSync('checked', 'change', { type: Boolean })
  readonly checkedValue!: boolean
}

is equivalent to

export default {
  model: {
    prop: 'checked',
    event: 'change',
  },
  props: {
    checked: {
      type: Boolean,
    },
  },
  computed: {
    checkedValue: {
      get() {
        return this.checked
      },
      set(value) {
        this.$emit('change', value)
      },
    },
  },
}

@ModelSync property can also set type property from its type definition via reflect-metadata .

@Watch(path: string, options: WatchOptions = {}) decorator

import { Vue, Component, Watch } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @Watch('child')
  onChildChanged(val: string, oldVal: string) {}

  @Watch('person', { immediate: true, deep: true })
  onPersonChanged1(val: Person, oldVal: Person) {}

  @Watch('person')
  onPersonChanged2(val: Person, oldVal: Person) {}
}

is equivalent to

export default {
  watch: {
    child: [
      {
        handler: 'onChildChanged',
        immediate: false,
        deep: false,
      },
    ],
    person: [
      {
        handler: 'onPersonChanged1',
        immediate: true,
        deep: true,
      },
      {
        handler: 'onPersonChanged2',
        immediate: false,
        deep: false,
      },
    ],
  },
  methods: {
    onChildChanged(val, oldVal) {},
    onPersonChanged1(val, oldVal) {},
    onPersonChanged2(val, oldVal) {},
  },
}

@Provide(key?: string | symbol) / @Inject(options?: { from?: InjectKey, default?: any } | InjectKey) decorator

import { Component, Inject, Provide, Vue } from 'vue-property-decorator'

const symbol = Symbol('baz')

@Component
export class MyComponent extends Vue {
  @Inject() readonly foo!: string
  @Inject('bar') readonly bar!: string
  @Inject({ from: 'optional', default: 'default' }) readonly optional!: string
  @Inject(symbol) readonly baz!: string

  @Provide() foo = 'foo'
  @Provide('bar') baz = 'bar'
}

is equivalent to

const symbol = Symbol('baz')

export const MyComponent = Vue.extend({
  inject: {
    foo: 'foo',
    bar: 'bar',
    optional: { from: 'optional', default: 'default' },
    baz: symbol,
  },
  data() {
    return {
      foo: 'foo',
      baz: 'bar',
    }
  },
  provide() {
    return {
      foo: this.foo,
      bar: this.baz,
    }
  },
})

@ProvideReactive(key?: string | symbol) / @InjectReactive(options?: { from?: InjectKey, default?: any } | InjectKey) decorator

These decorators are reactive version of @Provide and @Inject. If a provided value is modified by parent component, then the child component can catch this modification.

const key = Symbol()
@Component
class ParentComponent extends Vue {
  @ProvideReactive() one = 'value'
  @ProvideReactive(key) two = 'value'
}

@Component
class ChildComponent extends Vue {
  @InjectReactive() one!: string
  @InjectReactive(key) two!: string
}

@Emit(event?: string) decorator

The functions decorated by @Emit $emit their return value followed by their original arguments. If the return value is a promise, it is resolved before being emitted.

If the name of the event is not supplied via the event argument, the function name is used instead. In that case, the camelCase name will be converted to kebab-case.

import { Vue, Component, Emit } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  count = 0

  @Emit()
  addToCount(n: number) {
    this.count += n
  }

  @Emit('reset')
  resetCount() {
    this.count = 0
  }

  @Emit()
  returnValue() {
    return 10
  }

  @Emit()
  onInputChange(e) {
    return e.target.value
  }

  @Emit()
  promise() {
    return new Promise((resolve) => {
      setTimeout(() => {
        resolve(20)
      }, 0)
    })
  }
}

is equivalent to

export default {
  data() {
    return {
      count: 0,
    }
  },
  methods: {
    addToCount(n) {
      this.count += n
      this.$emit('add-to-count', n)
    },
    resetCount() {
      this.count = 0
      this.$emit('reset')
    },
    returnValue() {
      this.$emit('return-value', 10)
    },
    onInputChange(e) {
      this.$emit('on-input-change', e.target.value, e)
    },
    promise() {
      const promise = new Promise((resolve) => {
        setTimeout(() => {
          resolve(20)
        }, 0)
      })

      promise.then((value) => {
        this.$emit('promise', value)
      })
    },
  },
}

@Ref(refKey?: string) decorator

import { Vue, Component, Ref } from 'vue-property-decorator'

import AnotherComponent from '@/path/to/another-component.vue'

@Component
export default class YourComponent extends Vue {
  @Ref() readonly anotherComponent!: AnotherComponent
  @Ref('aButton') readonly button!: HTMLButtonElement
}

is equivalent to

export default {
  computed() {
    anotherComponent: {
      cache: false,
      get() {
        return this.$refs.anotherComponent as AnotherComponent
      }
    },
    button: {
      cache: false,
      get() {
        return this.$refs.aButton as HTMLButtonElement
      }
    }
  }
}

@VModel(propsArgs?: PropOptions) decorator

import { Vue, Component, VModel } from 'vue-property-decorator'

@Component
export default class YourComponent extends Vue {
  @VModel({ type: String }) name!: string
}

is equivalent to

export default {
  props: {
    value: {
      type: String,
    },
  },
  computed: {
    name: {
      get() {
        return this.value
      },
      set(value) {
        this.$emit('input', value)
      },
    },
  },
}