counter exapmle in vue js

// child component
Vue.component('counter', {
  template: `<div><button @click='add'>+1</button>
  <button @click='sub'>-1</button>
  <div>this is inside the child component: {{ result }}</div></div>`,
  data () {
    return {
      result: 0
    }
  },
  props: ['value'],
  methods: {
    emitResult () {
      this.$emit('input', this.result)
    },
    add () {
      this.result += 1
      this.emitResult()
    },
    sub () {
      this.result -= 1
      this.emitResult()
    }
  }  
})