我的JavaScript出现问题。这似乎很奇怪。这是怎么回事。我有一个表单,在用户提交表单后,它将调用一个函数(onsubmit事件)以验证提交的数据,如果出现问题,或者如果用户名/电子邮件已经存在于数据库中(此部分使用ajax),它将返回false并使用DOM显示错误。这是下面的代码。奇怪的是,它仅在我使用空的alert(’‘)消息时才起作用,没有它,它将不起作用。谢谢您的帮助。
////////////////////////////////////// function httpRequest() { var xmlhttp; if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); } else if (window.ActiveXObject) { // code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } else { alert("Your browser does not support XMLHTTP!"); } return xmlhttp; } function validateRegForm(reg) { var isValidForm = true; var warningIcon = "";//for later in case we want to use an icon next to warning msg with(reg) { var regFormDiv = document.getElementById("registration_form"); //Check if dynamic div exist, if so, remove it if(document.getElementById('disp_errors') != null) { var dispErrorsDiv = document.getElementById('disp_errors'); document.getElementById('reg_form').removeChild(dispErrorsDiv); } //Dynamically create new 'div' var errorDiv = document.createElement('div'); errorDiv.setAttribute('id','disp_errors'); errorDiv.setAttribute('style','background-color:pink;border:1px solid red;color:red;padding:10px;'); document.getElementById('reg_form').insertBefore(errorDiv,regFormDiv); var xmlhttp = httpRequest(); var available = new Array(); xmlhttp.onreadystatechange = function() { if(xmlhttp.readyState == 4) { var response = xmlhttp.responseText; if(response != "") { //Return values var newValue = response.split("|"); available[0] = newValue[0]; available[1] = newValue[1]; } } } xmlhttp.open("GET","profile_fetch_reg_info.php?do=available&un="+u_username.value+"&email="+u_email.value+"",true); xmlhttp.send(null); alert(' '); ////////////WITHOUT THIS, IT DOESN'T WORK. Why? if(available[1] == "taken") { errorDiv.innerHTML += warningIcon+'Username is already taken!<br />'; isValidForm = false; } else if(u_username.value.length < 4){ errorDiv.innerHTML += warningIcon+'Username must be more than 4 characters long!<br />'; isValidForm = false; } else if(u_username.value.length > 35) { errorDiv.innerHTML += warningIcon+'Username must be less than 34 characters long!<br />'; isValidForm = false; } if(available[0] == "taken") { errorDiv.innerHTML += warningIcon+'Email address entered is already in use!<br />'; isValidForm = false; } else if(u_email.value == ""){ errorDiv.innerHTML += warningIcon+'Email address is required!<br />'; isValidForm = false; } else { //Determine if email entered is valid var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/; if (!filter.test(u_email.value)) { errorDiv.innerHTML += warningIcon+'Email entered is invalid!<br />'; u_email.value = ""; isValidForm = false; } } if(u_fname.value == ""){ errorDiv.innerHTML = warningIcon+'Your first name is required!<br />'; isValidForm = false; } if(u_lname.value == ""){ errorDiv.innerHTML += warningIcon+'Your last name is required!<br />'; isValidForm = false; } if(u_password.value.length < 4){ errorDiv.innerHTML += warningIcon+'Password must be more than 4 characters long!<br />'; isValidForm = false; } else if(u_password.value.length > 35) { errorDiv.innerHTML += warningIcon+'Password must be less than 34 characters long!<br />'; isValidForm = false; } else if (u_password.value != u_password2.value) { errorDiv.innerHTML += warningIcon+'Password and re-typed password don\'t match!<br />'; isValidForm = false; } if(u_squestion.value == ""){ errorDiv.innerHTML += warningIcon+'A security question is required!<br />'; isValidForm = false; } if(u_sanswer.value == ""){ errorDiv.innerHTML += warningIcon+'A security answer is required!<br />'; isValidForm = false; } if(u_address.value == ""){ errorDiv.innerHTML += warningIcon+'Address is required!<br />'; isValidForm = false; } if(u_city.value == ""){ errorDiv.innerHTML += warningIcon+'City is required!<br />'; isValidForm = false; } if(u_state.value == ""){ errorDiv.innerHTML += warningIcon+'State is required!<br />'; isValidForm = false; } if(u_zip.value == ""){ errorDiv.innerHTML += warningIcon+'Zip code is required!<br />'; isValidForm = false; } if(u_phone.value == ""){ errorDiv.innerHTML += warningIcon+'Phone number is required!<br />'; isValidForm = false; } if(isValidForm == false) window.scroll(0,0); return isValidForm; } }
这有alert()帮助,因为这会延迟该函数中其余javascript的处理(从alert()下到下的所有操作),从而为AJAX请求留下足够的时间来完成。AJAX中的第一个字母代表“异步”,这意味着(默认情况下)响应将在“将来的某个时候”出现,但不是立即出现。
alert()
一个补丁修复(你应该 不 执行)是使处理同步(通过改变第三个参数open()是false),将停止脚本(以及整个网页)的进一步处理,直至请求返回。这很不好,因为它将有效地冻结Web浏览器,直到请求完成。
open()
false
正确的解决方法是重新组织代码,以便依赖AJAX请求结果的所有处理都可以进入该onreadystatechange函数,并且不能在启动AJAX请求的主函数中进行。
onreadystatechange
通常处理此方法的方法是修改您的DOM(在发送AJAX请求之前)以使表单变为只读状态并显示某种“处理中”消息,然后,如果一切正常,则在AJAX响应处理程序中(服务器正确响应) 并且 验证成功)submit()在表格上调用,否则使表格再次变为可写状态并显示任何验证错误。
submit()