优化联系表单的用户反馈：JavaScript与PHP交互逻辑深度解析

if(response.indexOf("Invalid email address!") || response.indexOf("Failed to send your message"))

const form = document.querySelector("form"),
      statusTxt = form.querySelector(".button-area span ");
// 定义一个常量来存储“正在发送”的文本
const sendingMsgText = 'Sending your message...';

form.onsubmit = (e) => {
   e.preventDefault(); // 阻止表单默认提交行为

   // 1. 在每次提交前，将状态文本重置为“正在发送...”
   statusTxt.style.color = "#1a66f1b1"; // 设置为蓝色或默认发送颜色
   statusTxt.style.display = "inline-block";
   statusTxt.innerText = sendingMsgText; // 确保显示“正在发送...”

   let xhr = new XMLHttpRequest();
   xhr.open("POST", "message.php", true);
   xhr.onload = () =>{
        if(xhr.readyState == 4 && xhr.status == 200){
            let response = xhr.response;

            // 2. 修正 indexOf() 的判断逻辑，检查是否不等于 -1
            if(response.indexOf("Invalid email address!") !== -1 || response.indexOf("Failed to send your message") !== -1)
            {
                statusTxt.style.color = "#ff4c29"; // 错误消息显示红色
            }
            else{
                form.reset(); // 成功发送后重置表单
                // 成功消息显示蓝色 (初始已设置，这里无需重复设置)
                setTimeout(() => {
                    statusTxt.style.display = "none"; // 3秒后隐藏状态文本
                }, 3000);
            }
            statusTxt.innerText = response; // 显示服务器返回的最终消息
        }
   }
   let formData = new FormData(form);
   xhr.send(formData);
}

const form = document.querySelector("form"),
      statusTxt = form.querySelector(".button-area span ");
const sendingMsgText = 'Sending your message...'; // 定义发送中消息文本

form.onsubmit = (e) => {
   e.preventDefault(); // 阻止表单默认提交行为

   // 在AJAX请求发送前，确保显示“正在发送...”状态
   statusTxt.style.color = "#1a66f1b1"; // 设置为发送中消息的颜色
   statusTxt.style.display = "inline-block";
   statusTxt.innerText = sendingMsgText; // 每次提交都重置为“正在发送...”

   let xhr = new XMLHttpRequest();
   xhr.open("POST", "message.php", true);
   xhr.onload = () =>{
        if(xhr.readyState == 4 && xhr.status == 200){
            let response = xhr.response;

            // 修正indexOf()判断逻辑：检查是否包含错误消息
            if(response.indexOf("Invalid email address!") !== -1 || response.indexOf("Failed to send your message") !== -1)
            {
                statusTxt.style.color = "#ff4c29"; // 错误消息显示红色
            }
            else{
                // 成功发送，重置表单并隐藏状态文本
                form.reset();
                setTimeout(() => {
                    statusTxt.style.display = "none";
                }, 3000);
            }
            statusTxt.innerText = response; // 显示服务器返回的最终消息
        }
   }
   let formData = new FormData(form);
   xhr.send(formData);
}