how to toggle class for multiple elements in vue js

Question

I'm trying to toggle classes for multiple elements in Vuejs 2.0, I have the following set of buttons which has a class of btn-primary. Clicking a button shows a sub-group of that particular element. This is my code:

<button class="btn btn-primary btn-xs" v-on:click.prevent="getTags('investor')">Investor</button>
<button class="btn btn-primary btn-xs" v-on:click.prevent="getTags('research')">Research</button>
<button class="btn btn-primary btn-xs" v-on:click.prevent="getTags('company')">Company</button>

This shows the following element:

<div v-if="tag.investor">
    <button class="btn btn-primary btn-xs" v-on:click.prevent="selectTags('Investor - Mutual Funds')">Mutual Fund</button>
    <button class="btn btn-primary btn-xs" v-on:click.prevent="selectTags('Investor - Insurance')">Insurance</button>
    <button class="btn btn-primary btn-xs" v-on:click.prevent="selectTags('Investor - FII')">FII</button>
</div>
<div v-if="tag.research">
    <button class="btn btn-primary btn-xs" v-on:click.prevent="selectTags('Research - Tier I')">Research - Tier I</button>
    <button class="btn btn-primary btn-xs" v-on:click.prevent="selectTags('Research - Tier II')">Research - Tier II</button>
</div>

I have the following in data():

tag: {
    investor: false,
    research: false,
    company: false,
    others: false,
 },

And in methods:

getTags: function (tag) {
    this.tag.investor = this.tag.research = this.tag.company = this.tag.others = false
    if(tag == 'investor')
    {
        this.tag.investor = true
    }
    if(tag == 'research')
    {
        this.tag.research = true
    }
    if(tag == 'company')
    {
        this.tag.company = true
    }
    if(tag == 'others')
    {
        this.tag.others = true
    }
},

I want to have a class of btn-warning and remove btn-primary once any child element is being selected. Any ideas how to implement this, I don't want to have individual data elements and toggle class.

Answer 1

I'd like to suggest a data driven approach for your Vue. Consider this data structure:

const tags = {
   Investor:[
     {display:"Mutual Fund", value:"Investor - Mutual Funds"},
     {display:"Insurance", value:"Investor - Insurance"},
     {display:"FII", value:"Investor - FII"},
   ],
   Research:[
     {display:"Research - Tier I", value:"Research - Tier I"},
     {display:"Research - Tier II", value:"Research - Tier II"},
  ]
}

If you use that, then you can clean up your template considerably and handle any additional tags that you add to your data structure.

<div id="app">
  <button v-for="(obj, key) in tags"
          :key="key"
          @click="currentTag = key"
          class="btn btn-xs btn-primary">
    {{key}}
  </button>

  <div>  
    <button v-for="tag in tags[currentTag]"
            :key="tag"
            class="btn btn-xs"
            :class="tagClass(tag)"
            @click="selectTags(tag.value)">
      {{tag.display}}
    </button>
  </div>
</div>

Your Vue also looks a lot cleaner.

new Vue({
  el:"#app",
  data:{
    currentTag: null,
    tags,
    selectedTags:[]
  },
  methods:{
    selectTags(tag){
      const index = this.selectedTags.findIndex(t => t == tag)

      if (index >= 0)
        this.selectedTags.splice(index, 1)
      else
        this.selectedTags.push(tag)
    },
    tagClass(tag){
      const isSelected = this.selectedTags.includes(tag.value)

      return {
        'btn-warning': isSelected,
        'btn-primary': !isSelected
      }
    }
  }
})

Here is an example.

Answer 2

You can use the v-bind:class directive.

<button 
  class="btn btn-xs" 
  v-bind:class="{ 'btn-warning': tag.research, 'btn-primary': !tag.research }"
  v-on:click.prevent="selectTags('Research - Tier I')"
>
  Research - Tier I
</button>