See the following function I have written
The code is to receive a url and send data to that page in post/get method.The function returns responseText from the target page
function $send(url,data,method)
{
if(window.XMLHttpRequest)
var connect = new XMLHttpRequest();
else
var connect = newActiveXObject("Microsoft.XMLHTTP");
if(connect)
{
method = method.toUpperCase();
if(method == 'GET')
{
url += '?'+data;
connect.open(method,url,true);
connect.send();
}
else
{
connect.setRequestHeader("Content-type","application/x-www-form-urlencoded");
connect.open(method,url,true);
connect.send(data);
}
connect.onreadystatechange = function()
{
alert(connect.readyState);
if(connect.readyState==4 &&connect.status == 200)
{
return connect.responseText ;
}
}
return "FALSE";
}
else
{
alert("$sendData() is not supported by your browser\n\nTRY ANOTHER BROWSER!!!");
return "FALSE";
}
}
As readstate is initially 0 and changes eventually,my function always return FALSE.Is there any way to return the responseText
Related
I need to send a ajax request to my server before web page close, my send code is below.
SendByAajx = function(msg) {
var response;
var xmlHttpReg;
if(window.XMLHttpRequest){
xmlHttpReg = new XMLHttpRequest();
} else if(window.ActiveXObject) {
xmlHttpReg = new ActiveXObject("Microsoft.XMLHTTP");
} else {
throw new Error("Unsupported borwser");
}
if(xmlHttpReg != null) {
xmlHttpReg.open("get", "https://127.0.0.1:57688/test"+'?'+msg, false);
xmlHttpReg.send(null);
if(xmlHttpReg.readyState==4){
if(xmlHttpReg.status == 200) {
var data = JSON.parse(xmlHttpReg.responseText);
if(typeof(data.errorcode) == "number" &&
data.errorcode != 0) {
throw("response error:" + data.errorcode);
}
response = data.result;
} else {
throw new Error("Error");
}
}
}
return response;
}
When I call this function in a button onclick event, it works.
function GetOnClick() {
try{
var result = SendByAajx (“data”);
} catch (e) {
//alert(errorInfo);
}
SetButtonDisabled(false);
}
But when I call this function when the page is unloaded, it doesn't work.
<body onload="javascript:OnLoad();" onunload="javascript:OnUnLoad()">
function OnUnLoad() {
try{
var result = SendByAajx(“data”);
} catch (e) {
//alert(errorInfo);
}
}
When I debug the application, the JS execution stops after this line:
xmlHttpReg.send(null);
It didn’t go to the next line:
if(xmlHttpReg.readyState==4)
The “data” is also not sent to the server.
What is wrong with my program, can ajax be called in an onunload function? What should I do to make it work?
ajax : function(typ,url,callback) {
if(window.XMLHttpRequest) {
var xml = new XMLHttpRequest();
}
if(window.ActiveXObject) {
var xml = new ActiveXObject("Microsoft.XMLHTTP");
}
xml.onreadystatechange = function(callback) {
if(xml.readyState == 4 && xml.status == 200) {
callback();
}
}
xml.open(typ,url,true);
xml.send();
}
}
//Function being called
window.onload = function() {
JS.ajax("GET","/server/chkEmail.php?email=email#email.com",function() {
alert(xml.responseText);
});
}
It throws the error saying:
Uncaught TypeError: callback is not a functionxml.onreadystatechange #
global.js:30
Any ideas?
I fixed it by passing the data variable through the onreadystatechange function and calling it in the callback function.
ajax : function(typ,url,callback) {
if(window.XMLHttpRequest) {
var xml = new XMLHttpRequest();
}
if(window.ActiveXObject) {
var xml = new ActiveXObject("Microsoft.XMLHTTP");
}
xml.onreadystatechange = function(data) {
if(xml.readyState == 4 && xml.status == 200) {
var data = xml.responseText;
callback(data);
}
};
xml.open(typ,url,true);
xml.send();
}
}
window.onload = function() {
JS.ajax("GET","/server/chkEmail.php? email=jonwcode#gmail.com",function(data){
alert(data);
});
}
Try like this:
xml.onreadystatechange = function() {
if (xml.readyState == 4 && xml.status == 200) {
callback();
}
};
Notice that the onreadystatechange function doesn't take any parameters whereas in your code you have passed it a parameter with the name callback which will override the callback variable from the outer scope.
UPDATE:
It looks like you have improperly scoped the xml variable and it isn't available in your AJAX callback. I strongly recommend you reading more about javascript variables scope. Here's how you could make the xml variable visible:
var xml = null;
if (window.XMLHttpRequest) {
xml = new XMLHttpRequest();
} else if (window.ActiveXObject) {
xml = new ActiveXObject("Microsoft.XMLHTTP");
}
if (xml == null) {
alert('Sorry, your browser doesn\'t seem to support AJAX - please upgrade to a modern browser');
} else {
xml.onreadystatechange = function() {
if(xml.readyState == 4 && xml.status == 200) {
var data = xml.responseText;
callback(data);
}
};
xml.open(typ,url,true);
xml.send();
}
I've seen the myriad threads sprawled across the Internet about the following similar code in an AJAX request returning undefined:
AJAX.onreadystatechange = function() {
if(AJAX.readyState == 4) {
if(AJAX.status == 200) {
var response = AJAX.responseText;
return response;
}
else {
window.alert('Error: ' + AJAX.status);
return false;
}
}
};
I know that I'm supposed to "do something with" responseText like writing it to the HTML. The problem: I don't have that luxury. This bit of code is intended to be inside of a generic method for running fast AJAX requests that way all the code for making an AJAX request doesn't have to written out over and over again (~40×) with the chance of a minor problem here or there that breaks the application.
My method HAS to explicitly return responseText "or else." No writing to HTML. How would I do this? Also, I'd appreciate a lack of plugs for JQuery.
What I'm looking for:
function doAjax(param) {
// set up XmlHttpRequest
AJAX.onreadystatechange = function() {
if(AJAX.readyState == 4) {
if(AJAX.status == 200) {
var response = AJAX.responseText;
return response;
}
else {
window.alert('Error: ' + AJAX.status);
return false;
}
}
};
// send data
}
...
function doSpecificAjax() {
var param = array();
var result = doAjax(param);
// manipulate result
}
Doing a little research I came across this SOF post:
Ajax responseText comes back as undefined
Based on that post, it looks like you may want to implement your ajax method like this:
function doRequest(url, callback) {
var xmlhttp = ....; // create a new request here
xmlhttp.open("GET", url, true); // for async
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4) {
if (xmlhttp.status == 200) {
// pass the response to the callback function
callback(null, xmlhttp.responseText);
} else {
// pass the error to the callback function
callback(xmlhttp.statusText);
}
}
}
xmlhttp.send(null);
}
Then, you can call that method like this...
doRequest('http://mysite.com/foo', function(err, response) { // pass an anonymous function
if (err) {
return "";
} else {
return response;
}
});
This should return the responseText accurately. Let me know if this doesn't give you back the correct results.
I have a simple ajax script which returns a json dump from the server:
var request = false;
try {
request = new XMLHttpRequest();
} catch (trymicrosoft) {
try {
request = new ActiveXObject("Msxml2.XMLHTTP");
} catch (othermicrosoft) {
try {
request = new ActiveXObject("Microsoft.XMLHTTP");
} catch (failed) {
request = false;
}
}
}
function getIslandName() {
var islandGroup = document.getElementById("id_island_group").value;
var url = ".../find_island?island_group=" + escape(islandGroup);
request.open("GET", url, true);
request.onreadystatechange = updatePage;
request.send(null);
}
function updatePage() {
if (request.readyState == 4)
if (request.status == 200)
var data = JSON.decode(request.responseText);
update(data);
//document.getElementById("ajax_response").innerHTML = request.responseText;
else if (request.status == 404)
alert("Request URL does not exist");
else
alert("Error: status code is " + request.status);
}
function update(data) {
for (var key in data) {
alert(data[key]);
}
}
The problem seems to be in the updatePage() function. If I uncomment this line:
//document.getElementById("ajax_response").innerHTML = request.responseText;
the responseText json dump is displayed as expected. e.g.:
["Foo Island", "Bar Island", "Darwin Island"]
Also if I construct a fresh data array within the updatePage() function like so:
function updatePage() {
var string = "Something something ajax";
if (request.readyState == 4)
if (request.status == 200)
var data=new Array();
data[0]="Foo Island";
data[1]="Bar Island";
data[2]="Darwin Island";
update(data);
}
The update() function works as expected and gives the expected alert output.
Any suggestions as to what I'm doing wrong will be much appreciated.
XmlHttpRequest works through callbacks. So how can I return a value? I tried to set a global variable, but that doesn't seem to be working.
var response = null; // contains the most recent XmlHttpRequest response
// loads the info for this username on the page
function loadUsernameInfo(username) {
getUserInfo(username);
var profile = response;
if (profile) {
// do stuff
}
else {
indicateInvalidUsername(username);
}
}
getUserInfo() can't return a result, because of the callback:
function getUserInfo(username) {
var request = createRequest();
request.onreadystatechange = userObjFromJSON;
var twitterURL = "http://twitter.com/users/show/" + escape(username) + ".json";
var url = "url.php?url=" + twitterURL;
request.open("GET", url, true);
request.send(null);
}
The callback:
function userObjFromJSON() {
if (this.readyState == 4) {
alert(this.responseText);
response = this.responseText;
}
}
How can I get the response back to loadUsernameInfo()?
You can do synchronous requests, though it is not recommended - the A is for Asynchronous... But the general idea to implement this correctly would be:
var response = null; // contains the most recent XmlHttpRequest response
// loads the info for this username on the page
function loadUsernameInfo(username) {
getUserInfo(username, onLoadUsernameComplete);
}
function getUserInfo(username, oncomplete) {
var request = createRequest();
request.__username = username;
request.onreadystatechange = oncomplete;
var twitterURL = "http://twitter.com/users/show/" + escape(username) + ".json";
var url = "url.php?url=" + twitterURL;
request.open("GET", url, true);
request.send(null);
}
function onLoadUsernameComplete(req) {
if (req.readyState == 4) {
// only if "OK"
if (req.status == 200) {
var profile = req.responseXML;
if (profile) {
// do stuff
}
else {
indicateInvalidUsername(req.__username);
}
}
}
}