bootstrap-vue/src/mixins/form-state.js

Quickly integrate Bootstrap 4 components with Vue.js

/* Form control contextual state class computation
 *
 * Returned class is either 'is-valid' or 'is-invalid' based on the 'state' prop
 * state can be one of five values:
 *  - true or 'valid' for is-valid
 *  - false or 'invalid' for is-invalid
 *  - null (or empty string) for no contextual state
 */

export default {
  props: {
    state: {
      // true/'valid', false/'invalid', '',null
      type: [Boolean, String],
      default: null
    }
  },
  computed: {
    computedState () {
      const state = this.state
      if (state === true || state === 'valid') {
        return true
      } else if (state === false || state === 'invalid') {
        return false
      }
      return null
    },
    stateClass () {
      const state = this.computedState
      if (state === true) {
        return 'is-valid'
      } else if (state === false) {
        return 'is-invalid'
      }
      return null
    }
  }
}