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how to properly use else if in javascript [duplicate]

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How do I return the response from an asynchronous call?
(41 answers)
Closed 2 years ago.
i have this script for submitting a form using jquery ajax, everything works fine except i can only get two responses, the loading part is implemented but the rest of them i can only get the else statement. the else if, none is working.
the json statement works just fine. and the data is passed to php successfully but the responses are not according.
(function($) {
'use strict';
const FormFunction = function(){
const checkSelectorExistence = function(selectorName) {
if(jQuery(selectorName).length > 0){return true;}else{return false;}
};
let registerForm = function() {
if(!checkSelectorExistence('.registration-form')){return;}
jQuery('.registration-form').on('submit', function( event ) {
event.preventDefault();
let response = $('.loading').addClass('show').show();
jQuery(this).find(".message").addClass('active').show('slow');
const formData = new FormData(this);
const formAction = jQuery(this).attr('action');
jQuery.ajax({
type: 'POST',
url: formAction,
data: formData,
contentType: false,
cache: false,
processData:false,
dataType: 'json',
beforeSend : function(){
$('.info').addClass('show').show('slow');
},
complete : function(){
$('.registration-form .message').html(response).delay(5000).hide('slow');
$('.registration-form')[0].reset();
},
success : function(data)
{
if(data.status === 1){
response = $('.success').addClass('show').show('slow');
}
else if(data.status === 2) {
response = $('.taken').addClass('show').show('slow');
}
else if(data.status === 0){
response = $('.empty').addClass('show').show('slow');
}
else {
response = $('.error').addClass('show').show('slow');
}
$('.registration-form .message').html(response).delay(5000).hide('slow');
$('.registration-form')[0].reset();
},
error : function(data){
$('.error').addClass('show').show('slow');
$('.registration-form')[0].reset();
},
});
});
}
/* Functions Calling */
return {
afterLoadThePage:function(){
registerForm();
},
}
}(jQuery);
/* jQuery Window Load */
jQuery(window).on("load", function (e) {FormFunction.afterLoadThePage();});
})(jQuery);

Based on some comments that we traded I managed to test it out and found out, what is the root of your problem. Even thought you are setting dataType as JSON, what you actually pass from PHP is a string of value "{\"status\":1}". This is currently the content of your data variable in Success function of your AJAX call.
Adding following line of code at begging of your Success function will do what you want it to do: data = JSON.parse(data);. This will parse string returned by PHP into an JSON object in JS which will create data.status instance holding desired value of number type.
I did some test on my end and it worked as expected with IF and ELSE IF as well.

CefSharp - Get result of AJAX request

I am really new to CefSharps Chromium browser and have difficulty figuring out how to get the result of a jquery ajax request.
My first attempt was to pass my AJAX requesto to EvaluateScriptAsync. In fact the script works. It does exactly what I want, but I do not get any results/status codes, because my Cef-Task does not wait until AJAX has completed its work.
Here an example (just a sample code):
var tasks = pdBrowser.EvaluateScriptAsync(#"
(function(){
$.ajax({
type: ""POST"",
dataType: ""json"",
cache: false,
url: ""_resources/php/ajaxRequests.php"",
async: false,
data: {
action: ""insertCrossPlatform"",
type: """",
values: JSON.stringify(""foo bar"")
},
success: function(response) {
if (typeof response === 'string' && response.substring(0, 5) == ""ERROR"")
{
return response;
}
else
{
//pageReload();
return ""OK"";
}
},
error: function(xhr, textStatus, errorThrown) {
return errorThrown + ""\n"" + xhr.responseText;
},
complete: function() {
return ""COMPLETE"";
}
});
})();", null);
tasks.ContinueWith(t =>
{
if (!t.IsFaulted)
{
var response = t.Result;
if (response.Success)
{
if (response.Result != null)
{
MessageBox.Show(response.Result.ToString());
}
}
else
{
MessageBox.Show(response.Message, "Ein Fehler ist aufgetreten", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
}
}, TaskScheduler.Default);
Afterwards I have read that there is a SchemeHandler, but I do not properly understand how to implement it. Can anyone help me out?
Thanks in advance.

Firstly SchemeHandler is unlikely to be suitable in this scenario, you would typically implement a SchemeHandler when your providing the response.
Most people choose to bind an object, and call a method on their bound object when they wish to communicate with the parent application. See the FAQ for an example. https://github.com/cefsharp/CefSharp/wiki/Frequently-asked-questions#3-how-do-you-expose-a-net-class-to-javascript
With 49.0.0 you can implement ResponseFilter to gain access to the underlying response buffer, it's complex and not well documented, so if your not comfortable digging through reference C++ code then this option isn't for you. Here's a reference https://github.com/cefsharp/CefSharp/blob/cefsharp/49/CefSharp.Example/Filters/PassThruResponseFilter.cs#L17

Something that I did was create an element on the page through javascript with an ID that is the response of the ajax call. So for example, when you make an ajax call assign an ID to the ajax call.
When the ajax call returns, write an element on the page with the pre-assigned id and callback information. Then you can just use cefsharp to read the element content from the page and this will be your callback information.
var myDivElement =document.getElementById('textareaInfo');
if( myDivElement === null)
{
var input = document.createElement('textarea');
input.id = "textareaInfo";
input.value = "Test"
input.rows="4";
input.cols="50";
input.style="height:100%;width:900px;"
var dom = document.getElementsByClassName("page-body")[0];
dom.insertAdjacentElement('afterbegin', input)
}
Then later with ajax
var root = 'https://jsonplaceholder.typicode.com';
var _holder = callbackObj;
callbackObj.showMessage(""ajax"");
$.ajax({
url: root + '/posts/1',
contentType: 'application/json; charset=utf-8',
method: 'GET',
complete: function(data){
},
success: function(response) {
$(#'textareaInfo').value(response);
}
}).then(function(data) {
callbackObj.showMessage(data);
});
Then read the texarea from cefsharp in c#
chromeBrowser.GetMainFrame().EvaluateScriptAsync(function()...$(textareaInfo).value).Result

You can use PostMessage javascript method to notify .NET application:
CefSharp.PostMessage('Your data Here');
Here is .NET code example for headless browser:
var browser = new ChromiumWebBrowser("", null, RequestContext);
browser.JavascriptMessageReceived += (sender, e) =>
{
if ((string)e.Message.notificationid == "notification1")
{
// Your processing code goes here
}
};
browser.Load(destinationUrl);
browser.ExecuteScriptAsync("(function() { ... ; CefSharp.PostMessage({data: data, notificationid: 'notification1'});})()");

SyntaxError: expected expression, got ')'

I've been stuck at this error for a few days and still couldn't figure out what is wrong. Would be great if someone could just point me to the right direction of solving this issue.
Update:
I realise that error is gone when I commented "addMessages(xml)" in the updateMsg() function. How do I make it work then?
Error:
http://i.imgur.com/91HGTpl.png
Code:
$(document).ready(function () {
var msg = $("#msg");
var log = $("#log");
var timestamp = 0;
$("#name").focus();
$("#login").click(function() {
var name = $("#name").val();
if (!name) {
alert("Please enter a name!");
return false;
}
var username = new RegExp('^[0-9a-zA-Z]+$');
if (!username.test(name)){
alert("Invalid user name! \n Please do not use the following characters \n `~!##$^&*()=|{}':;',\\[\\].<>/?~##");
return false;
}
$.ajax({
url: 'login.php',
type: 'POST',
dataType: 'json',
data: {name: name},
success: function() {
$(".login").hide();
}
})
return false;
});
$("#form").submit(function() {
if (!msg.val()) {
return false;
}
$.ajax({
url: 'add_message.php',
type: 'POST',
dataType: 'json',
data: {message: msg.val()},
})
msg.val("");
return false
});
window.setInterval(function () {
updateMsg();
}, 300);
function updateMsg() {
$.post('server.php', {datasize: '1024'}, function(xml) {
addMessages(xml);
});
}
function addMessages(xml) {
var json = eval('('+xml+')');
$.each(json, function(i, v) {
tt = parseInt(v.time);
if (tt > timestamp) {
console.log(v.message);
appendLog($("<div/>").text('[' + v.username + ']' + v.message));
timestamp = tt
}
});
}
function appendLog(msg) {
var d = log[0]
var doScroll = d.scrollTop == d.scrollHeight - d.clientHeight;
msg.appendTo(log)
if (doScroll) {
d.scrollTop = d.scrollHeight - d.clientHeight;
}
}
});

It might help to read up on eval a bit. It looks like it doesn't do what you think it does.
eval() is a dangerous function, which executes the code it's passed with the privileges of the caller.
Also
There are safer (and faster!) alternatives to eval() for common use-cases.
It looks like what you're trying to do is get data from the server in the form of JSON. You'll need to make sure that your server returns something that is valid JSON, which you can verify here. Most server-side programming languages have a library that will turn an object into JSON to make that a piece of cake. Here's an example for php.
On the client-side, you'll need to change var json = eval('(' + xml + ')'); to var json = JSON.parse(xml); This will give you the javascript version of your php/perl/python/etc object. If it's an array, you can then iterate through it with a for loop, Array.prototype.forEach, or a variety of functions from different libraries, such as $.each or _.each.

SyntaxError: expected expression, got ')' usually cause by something like
exeFunction(a,b,)
See if your form submit function ajax causing such error
$("#form").submit(function() {
if (!msg.val()) {
return false;
}
$.ajax({
url: 'add_message.php',
type: 'POST',
dataType: 'json',
data: {message: msg.val()}, <-------
})
msg.val("");
return false
});

If you are triggering the java script on click or trigger any click. sometimes missing of 0 gives the above error.
delete

would JSON.stringify({datasize: '1024'}) do the trick? just a guess

Parse XML catch block not catching exception in JS

I have a function that takes an XML file (obtained via AJAX) as input, parses it as XML and then execute some functions on it. A stripped down version can be found below.
AJAX
$.ajax({
type: "GET",
url: "./default.xml",
dataType: "xml",
success: function(data) {
parseMech(data);
}
});
parseMech function
function parseMech(xml) {
try {
var xmlObject = $(xml);
// See the output function below
$(".tree.base").html(treeBuilder(xmlObject.find("node").first()));
console.log("succes?");
} catch(e) {
$("#error-msg > .the-msg").text(" Invalid XML structure").parent().fadeIn(250);
console.log("Failed");
}
}
treeBuilder function
function treeBuilder(nodes) {
var newList = $("<ol>");
nodes.each(function (x, e) {
var newItem = $('<li> </li>');
for (var i = 0, l = e.attributes.length, a = null; i < l; i++) {
// Don't forget to add properties as data-attributes
a = e.attributes[i];
newItem.attr("data-" + a.nodeName, a.value);
if (a.nodeName == "cat" || a.nodeName == "word") {
newItem.html('' + a.value + '');
}
}
if ($(this).children('node').length) {
newItem.append(output($(this).children('node')));
}
newList.append(newItem);
});
return newList;
}
This works as it should when default.xml is a valid xml file. However, when it's not (for instance when I leave out a closing tag) the catch blok is not executed. In other words: when executing all functions with an invalid XML as source, neither console logs are executed, even though you would expect at least one (in try or in catch) to be logged.
Am I missing something here?

You need a fail handler in your ajax call.
According to the docs, a jquery ajax call with a dataType of xml returns a xml doc, so the data stream is being parsed in the course of the ajax call.
Alter the ajax call as follows (behaviour verified):
//...
error: function() {
console.log("ajax failed!");
},
//...
Note
Consider to change the way you specify your handlers,as error and success attributes are deprecated:
top.$.ajax({
type: "GET",
url: url,
crossDomain: true,
dataType: "xml",
})
.fail ( function() {
console.log("ajax failed!");
})
.done ( function(data) {
console.log("ajax ok!");
parseMech(data);
});

Callback with javascript and jquery

I am more of a java developer and am having difficulty with javascript callback. I am wondering if any experts here would help me out of my struggle with this code.
I am trying to pull our locations from db and populating in an array. On first load i am trying to refresh all locations and I am having trouble to control the flow of execution and loading values. Below is the code and I have put in the output at the end.
JQUERY CODE:
// load all locations on first load.
refreshLocations();
$("#locInput").autocomplete({source: locationData});
}); // end of document.ready
// function to refresh all locations.
function refreshLocations() {
getLocationArray(function(){
console.log("firing after getting location array");
});
}
// function to get the required array of locations.
function getLocationArray() {
getJsonValues("GET", "getLocalityData.php", "", getLocalityFromJson);
}
// function to pick up localities from json.
function getLocalityFromJson(json){
if (!json) {
console.log("====> JSON IS NOT DEFINED !! <====");
return;
} else {
console.log("json is defined so processing...");
var i = 0;
$.each(json.listinginfo, function() {
var loc = json.listinginfo[i].locality;
locationArray[i] = loc;
console.log("added location ->" + locationArray[i]);
i++;
});
}
//return locationArray;
}
// function to get raw json from db.
function getJsonValues(type, url, query, getLocalityFromJson) {
var json;
// if the previous request is still pending abort.
if (req !== null)
req.abort();
var searchString = "";
if (query !== "") {
searchString = "searchStr" + query;
}
console.log("searchString : (" + query + ")");
req = $.ajax({
type: type,
url: url,
data: searchString,
contentType: "application/json; charset=utf-8",
dataType: "text",
success: function(result) {
json = JSON.parse(result);
console.log("========start of json
return============");
console.log(JSON.stringify(json));
console.log("========end of json
return============");
//return json;
}
});
getLocalityFromJson(json);
return json;
}
the output from above code is as follows:
searchString : () (18:25:36:473)
at locality1.php:74
====> JSON IS NOT DEFINED !! <==== (18:25:36:518)
at locality1.php:48
========start of json return============ (18:25:37:606)
at locality1.php:83
{"listinginfo":[{"listing":"1","locality":"birmingham"},
{"listing":"2","locality":"oxford"}]} (18:25:37:624)
at locality1.php:84
========end of json return============ (18:25:37:642)
at locality1.php:85
>
Help will be greatly appreciated.

call getLocalityFromJson(json); inside your success callback
function getJsonValues(type, url, query, getLocalityFromJson) {
var json;
// if the previous request is still pending abort.
if (req !== null)
req.abort();
var searchString = "";
if (query !== "") {
searchString = "searchStr" + query;
}
console.log("searchString : (" + query + ")");
req = $.ajax({
type: type,
url: url,
data: searchString,
contentType: "application/json; charset=utf-8",
dataType: "text",
success: function(result) {
json = JSON.parse(result);
console.log("========start of json return============");
console.log(JSON.stringify(json));
console.log("========end of json return============");
//return json;
getLocalityFromJson(json);
}
});
}

You need to call getLocalityFromJson(json) and return json inside your ajax success function. Ajax requests are asynchronous, there's no guarantee that the request will be finished by the time you get to the lines getLocalityFromJson(json); return(json); where they are currently.

The call back functions from a jquery ajax call is complete, failure, success, etc..
Success is called after a request is successful,
Failure is called if theres something like an error 500, or a 404, or w/e.
Complete is Always called after a ajax call.
If you want your code to just follow sequence like in java, throw async: false into your ajax call.. but I wouldnt' recommend this as it defeats the purpose of using this method, and also locks up your browser.
You should make sure you are waiting for the request to finish before moving on - so put code in the success function that you want to run AFTER the request has finished fetching your data.

I think you need to remember Ajax is running async, so you need to follow this thread to execute your refresh.