[vue.js] Vue.js : How to set a unique ID for each component instance?

I want to create a component with Vue.js containing a label and an input. for example :

<label for="inputId">Label text</label>
<input id="inputId" type="text" />

How can I set a unique ID for each component instance?

Thank you.

To Nihat's point (above): Evan You has advised against using _uid: "The vm _uid is reserved for internal use and it's important to keep it private (and not rely on it in user code) so that we keep the flexibility to change its behavior for potential future use cases. ... I'd suggest generating UIDs yourself [using a module, a global mixin, etc.]"

Using the suggested mixin in this GitHub issue to generate the UID seems like a better approach:

let uuid = 0;

export default {
  beforeCreate() {
    this.uuid = uuid.toString();
    uuid += 1;
  },
};

Update: Code will throw an error if ._uid property does not exist in the instance so that you can update it to use something custom or new unique id property if provided by Vue.

Although zxzak's answer is great; _uid is not a published api property. To save a headache in case it changes in the future, you can update your code with just one change with a plugin solution like below.

Vue.use({
    install: function(Vue, options) {
        Object.defineProperty(Vue.prototype, "uniqId", {
            get: function uniqId() {
                if ('_uid' in this) {
                   return this._uid;
                }
                throw new Error("_uid property does not exist");
            }
        });
    }
});

npm i -S lodash.uniqueid

Then in your code...

<script>
  const uniqueId = require('lodash.uniqueid')

  export default {
    data () {
      return {
        id: ''
      }
    },
    mounted () {
       this.id = uniqueId()
    }
  }
</script>

This way you're not loading the entire lodash library, or even saving the entire library to node_modules.

Update

I published the vue-unique-id Vue plugin for this on npm.

Answer

None of the other solutions address the requirement of having more than one form element in your component. Here's my take on a plugin that builds on previously given answers:

Vue.use((Vue) => {
  // Assign a unique id to each component
  let uuid = 0;
  Vue.mixin({
    beforeCreate: function() {
      this.uuid = uuid.toString();
      uuid += 1;
    },
  });

  // Generate a component-scoped id
  Vue.prototype.$id = function(id) {
    return "uid-" + this.uuid + "-" + id;
  };
});

This doesn't rely on the internal _uid property which is reserved for internal use.

Use it like this in your component:

<label :for="$id('field1')">Field 1</label>
<input :id="$id('field1')" type="text" />

<label :for="$id('field2')">Field 2</label>
<input :id="$id('field2')" type="text" />

To produce something like this:

<label for="uid-42-field1">Field 1</label>
<input id="uid-42-field1" type="text" />

<label for="uid-42-field2">Field 2</label>
<input id="uid-42-field2" type="text" />

Use this: this.$options._scopeId - is the same identifier used in 'style scoped' section:

If you're using TypeScript, without any plugin, you could simply add a static id in your class component and increment it in the created() method. Each component will have a unique id (add a string prefix to avoid collision with another components which use the same tip)

<template>
  <div>
    <label :for="id">Label text for {{id}}</label>
    <input :id="id" type="text" />
  </div>
</template>

<script lang="ts">
  ...
  @Component
  export default class MyComponent extends Vue {
    private id!: string;
    private static componentId = 0;
    ...
    created() {
      MyComponent.componentId += 1;
      this.id = `my-component-${MyComponent.componentId}`;
    }
 </script>

In Vue2, use v-bind.

Say I have an object for a poll

  <div class="options" v-for="option in poll.body.options">
    <div class="poll-item">
      <label v-bind:for="option._id" v-bind:style="{color: option.color}">{{option.text}}</label>
      <input type="radio" v-model="picked" v-bind:value="option._id" v-bind:id="option._id">
  </div>
  </div>

This package seems to be a good solution for the underlying issue of having non-unique IDs in your DOM across multiple components:

vue-uniq-ids

It is a trend to use components. Components are cool, they are small, obvious, easy to use and modular. Untill it comes to the id property.

Some HTML tag attributes requires using an id property, like label[for], input[form] and many of aria-* attributes. And the problem with the id is that it is not modular. If several id properties on the page will has the same value they can affect each other.

VueUniqIds helps you to get rid of this problem. It provides the set of id-related directives which value is automatically modified by adding unique string while keeping the attrbitue easy to read.

If your uid is not used by other compoment, I have an idea.

uid: Math.random()

Simple and enough.

It can also be achieved using this pattern (Vue 2.0 v-bind) , so let say you have a list of items to iterate over and you want to give some dom element uninque id's.

new Vue({

  el:body,
  data: {
     myElementIds : [1,2,3,4,5,6,8]
   }
})

Html

<div v-for="id in myElementIds">
    <label v-bind:for="id">Label text for {{id}}</label>
    <input v-bind:id="id" type="text" />
<div> 

Hope it helps

A simple approach that I haven't seen in the replies is:

<template>
  <div>
    <label :for="id">Label text for {{id}}</label>
    <input :id="id" type="text" />
  </div>
</template>

<script>
import uniqueId from 'lodash-es/uniqueId'

export default {
  computed: {
    id () {
      # return this._uid
      return uniqueId('id')
    }
  }
}
</script>