beforecreate vuejs code example

Example 1: vuejs set

Vue.set(vm.someObject, 'propertyName', value)
// Or using alias
this.$set(this.someObject, 'propertyName', value)
// For an array, simply repalce propertyName with the index
this.$set(this.someArray, indexOfItem, value)
// Or assign new props to an object
this.someObject = Object.assign({}, this.someObject, { a: 1, b: 2 })

Example 2: vue watch

var vm = new Vue({
  el: '#demo',
  data: {
    firstName: 'Foo',
    lastName: 'Bar',
    fullName: 'Foo Bar'
  },
  watch: {
    firstName: function (val) {
      this.fullName = val + ' ' + this.lastName
    },
    lastName: function (val) {
      this.fullName = this.firstName + ' ' + val
    }
  }
})