详解如何在Vue中进行表单自定义验证

<template>
  <div>
    <label>用户名：</label>
    <input type="text" v-model="username" v-custom-validator:username.required="true">
    <div v-show="usernameError">{{ usernameErrorMessage }}</div>
    <label>密码：</label>
    <input type="password" v-model="password" v-custom-validator:password.required="true" v-custom-validator:password.minlength="6">
    <div v-show="passwordError">{{ passwordErrorMessage }}</div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      username: '',
      password: '',
      usernameError: false,
      passwordError: false,
      usernameErrorMessage: '',
      passwordErrorMessage: ''
    }
  },
  directives: {
    'custom-validator': {
      bind(el, binding) {
        const validator = binding.arg;
        const value = binding.value;
        const input = el;

        const checkValidity = () => {
          const isValid = validate(input.value, validator, value);
          if (isValid) {
            input.setCustomValidity('');
          } else {
            input.setCustomValidity(getErrorMessage(validator, value));
          }
        };

        input.addEventListener('input', checkValidity);
        input.addEventListener('blur', checkValidity);
      }
    }
  }
};

function validate(value, validator, arg) {
  switch (validator) {
    case 'required':
      return value.trim() !== '';
    case 'minlength':
      return value.trim().length >= arg;
    default:
      return true;
  }
}

function getErrorMessage(validator, arg) {
  switch (validator) {
    case 'required':
      return '该字段为必填项';
    case 'minlength':
      return `该字段长度不能少于${arg}个字符`;
    default:
      return '';
  }
}
</script>

<template>
  <div>
    <label>用户名：</label>
    <input type="text" v-model="username" v-custom-validator:username.required="true" v-custom-validator:username.minlength="6">
    <div v-show="usernameError">{{ usernameErrorMessage }}</div>
    <label>密码：</label>
    <input type="password" v-model="password" v-custom-validator:password.required="true" v-custom-validator:password.minlength="6">
    <div v-show="passwordError">{{ passwordErrorMessage }}</div>
    <button @click="submit" :disabled="isSubmitDisabled">提交</button>
  </div>
</template>

<script>
export default {
  data() {
    return {
      username: '',
      password: '',
      usernameError: false,
      passwordError: false,
      usernameErrorMessage: '',
      passwordErrorMessage: ''
    }
  },
  directives: {
    'custom-validator': {
      bind(el, binding) {
        const validator = binding.arg;
        const value = binding.value;
        const input = el;

        const checkValidity = (combineValidator) => {
          const isValid = validate(input.value, validator, value, combineValidator);
          if (isValid) {
            input.setCustomValidity('');
          } else {
            input.setCustomValidity(getErrorMessage(validator, value));
          }
        };

        input.addEventListener('input', () => checkValidity(false));
        input.addEventListener('blur', () => checkValidity(false));
        input.addEventListener('change', () => checkValidity(true));
      }
    }
  },
  computed: {
    isSubmitDisabled() {
      return this.usernameError || this.passwordError;
    }
  },
  methods: {
    submit() {
      // 提交表单
    }
  }
};

function validate(value, validator, arg, combineValidator) {
  switch (validator) {
    case 'required':
      return value.trim() !== '';
    case 'minlength':
      return value.trim().length >= arg;
    default:
      if (combineValidator) {
        return validate(value, 'required', true) && validate(value, 'minlength', arg);
      }
      return true;
  }
}

function getErrorMessage(validator, arg) {
  switch (validator) {
    case 'required':
      return '该字段为必填项';
    case 'minlength':
      return `该字段长度不能少于${arg}个字符`;
    default:
      return '';
  }
}
</script>