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Check(validate) send form data with ajax

I,m try check(validate) form data by using AJAX.
First i create callback function with AJAX request(in my example it's field time)
When i found same record in database, my NodeJS server response with value false, it's means we have record and we don't need add second record with that time).
My problem is that the form is still sent, regardless of the server response.
here my code(front end)
function funABC(mdata,callback){
console.log(mdata);
$.ajax({
url:'/dashboard/materials/checkshowrange',
method: 'GET',
dataType: "json",
contentType: "application/json",
data:mdata,
success: callback ,
// error:callback,
});
}
$('.addForm').on('submit', function (event) {
let form = $('.addForm');
if (form[0].checkValidity() === false) {
event.preventDefault();
event.stopPropagation();
// return false;
}
event.preventDefault();
checkdata = {
time_show : document.querySelector('.addForm').elements.time_show.value
}
functABC(checkdata,function(result) {
console.log(result);
if (result == 'true') {
alert(`For time: ${checkdata. time_show} there is already an event, choose a different time`);
return false;
}
})
form.addClass('was-validated');
some operations with form data, then send with ajax
$.ajax({
type: "POST",
url: "/dashboard/materials/add",
dataType: "json",
contentType: "application/json",
success: function (data) {
setTimeout(location.href = '/dashboard/materials', 10000);
},
data: JSON.stringify(formdata)
});
});

How and where did you call that post request ?
May be you would need to move post request into the callback
function funABC(mdata, callback) {
console.log(mdata);
$.ajax({
url: '/dashboard/materials/checkshowrange',
method: 'GET',
dataType: "json",
contentType: "application/json",
data: mdata,
success: callback,
// error:callback,
});
}
$('.addForm').on('submit', function(event) {
let form = $('.addForm');
if (form[0].checkValidity() === false) {
event.preventDefault();
event.stopPropagation();
// return false;
}
event.preventDefault();
checkdata = {
time_show: document.querySelector('.addForm').elements.time_show.value
}
functABC(checkdata, function(result) {
console.log(result);
if (result == 'true') {
alert(`For time: ${checkdata. time_show} there is already an event, choose a different time`);
return false;
} else {
$.ajax({
type: "POST",
url: "/dashboard/materials/add",
dataType: "json",
contentType: "application/json",
success: function(data) {
setTimeout(location.href = '/dashboard/materials', 10000);
},
data: JSON.stringify(formdata)
});
}
})
form.addClass('was-validated');
});
Or you could async false for validation request
$.ajax({
url: '/dashboard/materials/checkshowrange',
method: 'GET',
dataType: "json",
contentType: "application/json",
data: mdata,
success: callback,
async: false,
// error:callback,
});

Html for response when i want a string

I have the function below:
function getHtmlFromMarkdown(markdownFormat, requestUrl) {
const dataValue = { "markdownFormat": markdownFormat }
$.ajax({
type: "POST",
url: requestUrl,
data: dataValue,
contentType: "application/json: charset = utf8",
dataType: "text",
success: function (response) {
alert(response);
document.getElementById("generatedPreview").innerHTML = response;
},
fail: function () {
alert('Failed')
}
});
}
And i have this on my server:
[WebMethod]
public static string GenerateHtmlFromMarkdown(string markdownFormat)
{
string htmlFormat = "Some text";
return htmlFormat;
}
I have on response html code, not the string that i want. What am I doing wrong?
And if i change the "dataType: json" it doesn't even enter either the success nor fail functions

Your data type of ajax must be json like this
function getHtmlFromMarkdown(markdownFormat, requestUrl) {
var dataValue = { "markdownFormat": markdownFormat }
$.ajax({
type: "POST",
url: requestUrl,
data: JSON.stringify(dataValue),
dataType: "json",
success: function (response) {
alert(response);
document.getElementById("generatedPreview").innerHTML = response;
},
error: function () { alert("Failed"); }
});
}

try with this.
function getHtmlFromMarkdown(markdownFormat, requestUrl) {
var obj={};
obj.markdownFormat=markdownFormat;
$.ajax({
type: "POST",
url: requestUrl,
data: JSON.stringify(obj),
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (response) {
alert(response.d);
document.getElementById("generatedPreview").innerHTML = response.d;
},
failure: function () {
alert('Failed')
}
});
}

ajax jquery message show after the function completed

I think it is simple question. I've tried to search but still not found an answer yet.
deleteComment: function (commentJson, success, error) {
$.ajax({
type: "POST",
async: false,
url: deleteCommentConfig.url,
contentType: "application/json; charset=utf-8",
data: JSON.stringify({ commentId: commentJson.CommentId }),
dataType: "json",
success: function (result) {
if (result.d) {
success();
}
messageBox(result.d);
},
error: error
});
},
var messageBox = function (hasDeleted) {
if (hasDeleted) {
alert("Deleted successfully");
} else {
alert("Error");
}
}
I want to show message after success() performed.
That means the comment left already then show message.
Thanks anyway!
P/s: I read a topic about jQuery Callback Functions at https://www.w3schools.com/jquery/jquery_callback.asp.
Can we use it in here? If we can, how to use?

You can try like this
deleteComment: function (commentJson, success, error) {
$.ajax({
type: "POST",
async: false,
url: deleteCommentConfig.url,
contentType: "application/json; charset=utf-8",
data: JSON.stringify({ commentId: commentJson.CommentId }),
dataType: "json",
success: function (result) {
if (result.d) {
success();
}
$.when(this).then(setTimeout(function(){ messageBox(result.d)}, 200));
// if you dont want use set timeout then use
// $.when(this).then(messageBox(result.d), 200));
},
error: error
});
},
var messageBox = function (hasDeleted) {
if (hasDeleted) {
alert("Deleted successfully");
} else {
alert("Error");
}
}
Provides a way to execute callback functions based on zero or more Thenable objects, usually Deferred objects that represent asynchronous events.

Considering your implementation of var success = function() you may try with following approach:
Modify the success() to accept callback function as follows:
var success = function(callback) {
self.removeComment(commentId);
if(parentId)
self.reRenderCommentActionBar(parentId);
if(typeof callback == "function")
callback();
};
var messageBox = function (hasDeleted) {
if (hasDeleted) {
alert("Deleted successfully");
} else {
alert("Error");
}
}
deleteComment: function (commentJson, success, error) {
$.ajax({
type: "POST",
async: false,
url: deleteCommentConfig.url,
contentType: "application/json; charset=utf-8",
data: JSON.stringify({ commentId: commentJson.CommentId }),
dataType: "json",
success: function (result) {
if (result.d) {
//passing the callback function to success function
success(function(){
messageBox(result.d);
});
}
},
error: error
});
},

Call ajax.fail() from ajax.success()

So all I want to do is conditionally call the .fail method from within the .success method, how?
var ajaxCall = $.ajax({
url: pUrl,
type: "POST",
data: pData,
dataType: "json",
processData: false,
contentType: "application/json; charset=utf-8"
})
.always(function () {
alert("always");
})
.success(function (data) {
if (data == "fail") { ajaxCall.fail(); return; }
alert("success");
})
.fail(function () {
alert("fail");
});

$.ajax return a promise so you can't do it directly. Your best shot is that :
var fail = function () {
alert("fail");
};
var ajaxCall = $.ajax({
url: pUrl,
type: "POST",
data: pData,
dataType: "json",
processData: false,
contentType: "application/json; charset=utf-8"
})
.always(function () {
alert("always");
})
.success(function (data) {
if (data == "fail") { fail(); return; }
alert("success");
})
.fail(fail);

You can simply call as this.fail(); as shown below :-
var ajaxCall = $.ajax({
url: pUrl,
type: "POST",
data: pData,
dataType: "json",
processData: false,
contentType: "application/json; charset=utf-8"
})
.always(function () {
alert("always");
})
.success(function (data) {
if (data == "fail")
{
this.fail();
return;
}
alert("success");
})
.fail(function () {
alert("fail");
});
For more information :-
http://www.youlikeprogramming.com/2013/07/jqueryajax-conditionally-call-error-method-fro-success/

just use the "this" keyword to actually call any other method of the ajax call, I have made a sample for error method.
$.ajax({
url: 'url',
dataType: 'json',
contentType: 'application/json; charset=utf-8;',
type: 'GET',
success: function (dataReturn) {
this.error('error called explicitly');
},
error: function (errorMessage) {
if(errorMessage.ResponseText) // or directly compare as errorMessage !== "error called explicitly" if u send the same message elsewhere
//actual error code
else
alert(errorMessage);
}
});
hope this helps :)

why does returning the jquery AJAX promise in this function fail to give me the data?

This AJAX works on jsfiddle
var a = $.ajax({
url: "/echo/json/",
type: "post",
data: {
json: JSON.stringify({
a: true
})
},
dataType: "json"
});
a.done(function (data) {
console.log(data);
});
Why won't it work when I make a the function and return the AJAX promise?
var a = function () {
return $.ajax({
url: "/echo/json/",
type: "post",
data: {
json: JSON.stringify({
a: true
})
},
dataType: "json"
});
}
a.done(function (data) {
console.log(data);
});
Is this not the correct syntax? Well, apparently not, but how can I build the AJAX request into the function? FIDDLE

Since a is a function, you have to call it:
a().done(function(data) {
console.log(data);
});