HowTo使用新的错误消息创建自定义MaxLength和所需的验证，逻辑保持不变

要创建自定义的最大长度（MaxLength）和必填（Required）验证错误消息，你可以使用多种方法，具体取决于你使用的前端框架或库。以下是一些常见的前端框架和库的示例：

1. HTML5表单验证

HTML5提供了内置的表单验证功能，可以通过设置maxlength和required属性来实现基本的验证。对于自定义错误消息，可以使用JavaScript来覆盖默认行为。

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Custom Validation Messages</title>
<script>
function validateForm() {
    var input = document.forms["myForm"]["myInput"].value;
    if (input.length > 10) {
        alert("Maximum length exceeded: only 10 characters allowed.");
        return false;
    }
    if (input == "") {
        alert("This field is required.");
        return false;
    }
}
</script>
</head>
<body>
<form name="myForm" onsubmit="return validateForm()" method="post">
    <label for="myInput">Enter text:</label>
    <input type="text" id="myInput" name="myInput" maxlength="10" required>
    <input type="submit" value="Submit">
</form>
</body>
</html>

2. React.js

在React中，你可以使用受控组件和状态管理来实现自定义验证。

import React, { useState } from 'react';

function CustomValidationForm() {
    const [value, setValue] = useState('');
    const [errors, setErrors] = useState({});

    const handleChange = (e) => {
        setValue(e.target.value);
    };

    const handleSubmit = (e) => {
        e.preventDefault();
        let formErrors = {};
        if (value.length > 10) {
            formErrors.maxLength = "Maximum length exceeded: only 10 characters allowed.";
        }
        if (!value) {
            formErrors.required = "This field is required.";
        }
        setErrors(formErrors);
        if (Object.keys(formErrors).length === 0) {
            // Submit the form
        }
    };

    return (
        <form onSubmit={handleSubmit}>
            <label>Enter text:</label>
            <input type="text" value={value} onChange={handleChange} />
            {errors.maxLength && <p>{errors.maxLength}</p>}
            {errors.required && <p>{errors.required}</p>}
            <button type="submit">Submit</button>
        </form>
    );
}

export default CustomValidationForm;

3. Vue.js

在Vue.js中，你可以使用计算属性和方法来实现自定义验证。

<template>
  <form @submit.prevent="submitForm">
    <label>Enter text:</label>
    <input type="text" v-model="inputValue" />
    <p v-if="errors.maxLength">{{ errors.maxLength }}</p>
    <p v-if="errors.required">{{ errors.required }}</p>
    <button type="submit">Submit</button>
  </form>
</template>

<script>
export default {
  data() {
    return {
      inputValue: '',
      errors: {}
    };
  },
  methods: {
    submitForm() {
      this.errors = {};
      if (this.inputValue.length > 10) {
        this.errors.maxLength = "Maximum length exceeded: only 10 characters allowed.";
      }
      if (!this.inputValue) {
        this.errors.required = "This field is required.";
      }
      if (Object.keys(this.errors).length === 0) {
        // Submit the form
      }
    }
  }
};
</script>