[英]ajax success callback executes out of expected order
我有一个可以在按下按钮时验证某些字段的功能。 第一个检查用户名和密码是否真实。 那么如果密码是适当安全的。 然后,如果它与确认密码框匹配。 但是,在弹出第一个功能中的警报之前,似乎无法完成检查用户是否真实的ajax。
$(document).ready(function() {
$('#submit_pw_ch').on('click', function(){
var alertString = "Please correct the following errors: \n"
//current username and password are correct
var vUsr = valUsr();
//new password is sufficiently secure
var vPwd = valPwd();
//confirmation of new password is same as previous box
var sPwd = samePwd();
console.log('valid user : ' + vUsr + ' valid password : ' + vPwd + ' same password : ' + sPwd);
//append appropriate warnings to alert string
if ( !vUsr ) { alertString += "-Your current username and password are invalid. \n"; }
if ( !vPwd ) { alertString += "-The new password you have selected is not strong enough. \n"; }
if ( !sPwd ) { alertString += "-The confirmation of your new password does not match the previous entry. \n"; }
if ( !vUsr || !vPwd || !sPwd ) {
alert(alertString);
return false;
} else {
//change password
}
});
});
所以检查的那一行是var vUsr = valUsr();
哪个电话
function valUsr() {
var un = $('#uNameInput').val();
var pw = $('#uPwdInput').val();
//return value
var validUsr = false;
$.ajax({
type: "post",
url: "queries/confirm_user.php?<?=time()?>",
data: "un=" + un + "&pw=" + pw,
dataType: "json",
success: function (returnedData) {
console.log(returnedData)
if (data == 'true') {
validUsr = true;
} else {
validUsr = false;
}
}
});
return validUsr;
}
尽管警报不知何故不等待ajax完成获取数据。 我关闭警报框后, valUsr()
函数中的console.log(returnedData)
出现在控制台中。 为什么会这样呢? 我该如何预防? 谢谢!
托马斯
您需要满足ajax固有的异步性,换句话说,您需要等到对ajax请求的响应到达后再决定要做什么。
jQuery的Deferreds (和Promise)使我们可以编写简单的代码,但是Deferreds乍一看会引起您的注意,至少非常轻微。
对于这种问题,没有使用递延的唯一方法,但这是一个方法。
$(document).ready(function() {
$('#submit_pw_ch').on('click', function() {
var form = this.form; //the form containing the submit button and the fields .
//`alertArr` is an array to which messages will be added.
var alertArr = ["Please correct the following errors:"];
//`addAlert` will be called from a `Deferred.resolveWith(this, ...)` statement.
//The context, `this`, is unused.
function addAlert(index, txt) {
alertArr[index] = txt;
}
//`compositeAction` will be called from a promise.done() statement.
function compositeAction() {
//first filter out null messages (ie. validation successes) from alertArr.
var message = $.map(alertArr, function(txt, i){
return txt || null;
});
if(message.length > 1) {
//then alert the complete message with line breaks
alert(message.join("\n"));
} else {
//submit the form to change the password
//or another ajax call as required
form.submit();
}
}
// Invoke ajax validators and assign returned promises.
// An index is passed, so the text messages can be displayed in a logical order,
// regardless of the order in which the validation promises are resolved.
//If we didn't care about the order of the messages then the code would be slighly simpler.
var vUsr = valUsr(0),
vPwd = valPwd(1),
sPwd = samePwd(2);
//All validations adopt a similar pattern regardless of whether ajax is involved or not.
//Here, we establish what is to be done when the promise are resolved, or
//what is to be done immediately if the promise are alrady resolved.
vUsr.done(addAlert);
vPwd.done(addAlert);
sPwd.done(addAlert);
//At this stage, `addAlert` will contain entries for successful as well as unsuccessful validations. Successful entries will be filtered out by `compositeAction`
//Establish what is to be done when all three promises are resolved.
$.when(vUsr, vPwd, sPwd).done(compositeAction);
//Return false unconditionally
return false;
});
function valUsr(index) {
var messages = {
validated: '',//important - this message must be an empty string - do not change
notValidated: '- Your current username and password are invalid.',
ajaxError: '- Validation error: username and password.'
};
//Create a Deferred object, which will be resolved in response to several different outcomes.
var def = $.Deferred();
$.ajax({
type: "post",
url: "queries/confirm_user.php?<?=time()?>",
data: {
'un': $('#uNameInput').val(),
'pw': $('#uPwdInput').val()
},
dataType: "json",
success: function (returnedData) {
if (returnedData == 'true') {
def.resolveWith(this, [index, messages.validated]);
} else {
def.resolveWith(this, [index, messages.notValidated]);
}
},
error: function() {
def.resolveWith(this, [index, messages.ajaxError]);
}
});
return def.promise();//Return a promise derived from the as yet unresolved Deferred.
}
function samePwd(index) {
var pw1 = $('#uPwdInput').val();
var pw2 = $('#uPwdInput2').val();
var errMessage = (pw1 === pw2) ? '' : '-The confirmation of your new password does not match the previous entry';
var def = $.Deferred();//Create a Deferred object, which will be resolved immediately
def.resolveWith(this, [index, errMessage]);
return def.promise();//Return a promise derived from the already resolved Deferred.
}
});
valPwd()
的格式将与valUsr()
或samePwd()
,具体取决于是否涉及ajax。
成功回调中的ajax请求完成后 ,您将需要检查其他字段的有效性。 您可以关闭同步请求,但浏览器将冻结直到它得到一个为止,不建议这样做。
您将需要重新组织呼叫以反映这一点; 我建议他们在完成密码输入后立即将字段发送给您,要求您检查一下。 这样,如果有任何错误,您将可以避免等待表格末尾的时间。
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