XMLHttpRequest , buka sebuah URL dan kirim request tersebut. setelah transaksi selesai, objek akan berisi informasi yang berguna seperti badan respon dan status HTTP dari hasilnya.function reqListener () {
console.log(this.responseText);
}
var oReq = new XMLHttpRequest();
oReq.addEventListener("load", reqListener);
oReq.open("GET", "http://www.example.org/example.txt");
oReq.send();
Sebuh request yang dihasilkan melalui XMLHttpRequest dapat mengambil data dari salah satu cara, asynchronously or synchronously. Tipe dari request ditentukan onleh opsi async argument (argument ke-tiga) yang telah diset dialam metode {{domxref("XMLHttpRequest.open()")}}. Jika argument tersebut true atau tidak ditentukan. XMLHttpRequest akan diproses secara asynchronous,jika tidak proses akan berjalan secara synchronous. Diskusi detail dan demonstrasi dari kedua cara merequest tersebut dapat ditemukan pada halaman synchronous and asynchronous requests. Jangan gunakan permintaan synchronous di luar Pekerja Web.
XMLHttpRequest tidak terbatas hanya pada dokumen XML. Itu dimulai dengan "XML" karena ketika itu dibuat format utama yang awalnya digunakan untuk Asynchronous Data Exchange adalah XMLAda beberapa jenis atribut respons ditentukan oleh spesifikasi standar untuk {domxref("XMLHttpRequest.XMLHttpRequest", "XMLHttpRequest()")}} constructor. Ini memberi tahu klien membuat informasi penting XMLHttpRequest tentang status respons. Beberapa kasus di mana berurusan dengan jenis respons non-teks mungkin melibatkan beberapa manipulasi dan analisis diuraikan dalam bagian berikut.
Jika kamu mengunakan XMLHttpRequest untuk mendapatkan konten dokumen XML jarak jauh, properti {{domxref("XMLHttpRequest.responseXML", "responseXML")}} akan menjadi objek DOM yang berisi dokumen XML parsing. Ini terbentuk sulit untuk dimanipulasi dan dianalisis. Ada empat cara utama untuk menganalisis dokumen XML ini:
Note: XMLHttpRequest sekarang dapat menafsirkan HTML untuk Anda menggunakan properti {{domxref("XMLHttpRequest.responseXML", "responseXML")}}. Baca artikel HTML dalam XMLHttpRequest untuk mempelajari cara untuk melakukannya.
Jika kamu mengunakan XMLHttpRequest untuk mendapatkan konten dari halaman web HTML jarak jauh. Properti {{domxref("XMLHttpRequest.responseText", "responseText")}} adalah sebuah string yang berisi data HTML mentah. Hal ini terbukti sulit untuk dimanipulasi dan dianalisi. Karenanya ada tiga cara utama untuk
If you use XMLHttpRequest to get the content of a remote HTML webpage, the {{domxref("XMLHttpRequest.responseText", "responseText")}} property is a string containing the raw HTML. This could prove difficult to manipulate and analyze. Ada tiga cara utama untuk menganalisis dan mengurai string HTML mentah ini:
XMLHttpRequest.responseXML property as covered in the article HTML in XMLHttpRequest.fragment.body.innerHTML and traverse the DOM of the fragment.responseText beforehand. You might want to remove line breaks, if you use RegExp to scan with regard to linebreaks. However, this method is a "last resort" since if the HTML code changes slightly, the method will likely fail.Although {{domxref("XMLHttpRequest")}} is most commonly used to send and receive textual data, it can be used to send and receive binary content. There are several well tested methods for coercing the response of an XMLHttpRequest into sending binary data. These involve utilizing the {{domxref("XMLHttpRequest.overrideMimeType", "overrideMimeType()")}} method on the XMLHttpRequest object and is a workable solution.
var oReq = new XMLHttpRequest();
oReq.open("GET", url);
// retrieve data unprocessed as a binary string
oReq.overrideMimeType("text/plain; charset=x-user-defined");
/* ... */
However, more modern techniques are available, since the {{domxref("XMLHttpRequest.responseType", "responseType")}} attribute now supports a number of additional content types, which makes sending and receiving binary data much easier.
For example, consider this snippet, which uses the responseType of "arraybuffer" to fetch the remote content into a {{jsxref("ArrayBuffer")}} object, which stores the raw binary data.
var oReq = new XMLHttpRequest();
oReq.onload = function(e) {
var arraybuffer = oReq.response; // not responseText
/* ... */
}
oReq.open("GET", url);
oReq.responseType = "arraybuffer";
oReq.send();
For more examples check out the Sending and Receiving Binary Data page
XMLHttpRequest provides the ability to listen to various events that can occur while the request is being processed. This includes periodic progress notifications, error notifications, and so forth.
Support for DOM {{event("progress")}} event monitoring of XMLHttpRequest transfers follows the specification for progress events: these events implement the {{domxref("ProgressEvent")}} interface. The actual events you can monitor to determine the state of an ongoing transfer are:
responsevar oReq = new XMLHttpRequest();
oReq.addEventListener("progress", updateProgress);
oReq.addEventListener("load", transferComplete);
oReq.addEventListener("error", transferFailed);
oReq.addEventListener("abort", transferCanceled);
oReq.open();
// ...
// progress on transfers from the server to the client (downloads)
function updateProgress (oEvent) {
if (oEvent.lengthComputable) {
var percentComplete = oEvent.loaded / oEvent.total * 100;
// ...
} else {
// Unable to compute progress information since the total size is unknown
}
}
function transferComplete(evt) {
console.log("The transfer is complete.");
}
function transferFailed(evt) {
console.log("An error occurred while transferring the file.");
}
function transferCanceled(evt) {
console.log("The transfer has been canceled by the user.");
}
Lines 3-6 add event listeners for the various events that are sent while performing a data transfer using XMLHttpRequest.
open() on the request. Otherwise the progress events will not fire.The progress event handler, specified by the updateProgress() function in this example, receives the total number of bytes to transfer as well as the number of bytes transferred so far in the event's total and loaded fields. However, if the lengthComputable field is false, the total length is not known and will be zero.
Progress events exist for both download and upload transfers. The download events are fired on the XMLHttpRequest object itself, as shown in the above sample. The upload events are fired on the XMLHttpRequest.upload object, as shown below:
var oReq = new XMLHttpRequest();
oReq.upload.addEventListener("progress", updateProgress);
oReq.upload.addEventListener("load", transferComplete);
oReq.upload.addEventListener("error", transferFailed);
oReq.upload.addEventListener("abort", transferCanceled);
oReq.open();
file: protocol.Note: Starting in {{Gecko("9.0")}}, progress events can now be relied upon to come in for every chunk of data received, including the last chunk in cases in which the last packet is received and the connection closed before the progress event is fired. In this case, the progress event is automatically fired when the load event occurs for that packet. This lets you now reliably monitor progress by only watching the "progress" event.
Note: As of {{Gecko("12.0")}}, if your progress event is called with a responseType of "moz-blob", the value of response is a {{domxref("Blob")}} containing the data received so far.
One can also detect all three load-ending conditions (abort, load, or error) using the loadend event:
req.addEventListener("loadend", loadEnd);
function loadEnd(e) {
console.log("The transfer finished (although we don't know if it succeeded or not).");
}
Note there is no way to be certain, from the information received by the loadend event, as to which condition caused the operation to terminate; however, you can use this to handle tasks that need to be performed in all end-of-transfer scenarios.
Instances of XMLHttpRequest can be used to submit forms in two ways:
Using the FormData API is the simplest and fastest, but has the disadvantage that data collected can not be stringified.
Using only AJAX is more complex, but typically more flexible and powerful.
XMLHttpRequestSubmitting forms without the FormData API does not require other APIs for most use cases. The only case where you need an additional API is if you want to upload one or more files, where you use the {{domxref("FileReader")}} API.
An html {{ HTMLElement("form") }} can be sent in four ways:
POST method and setting the enctype attribute to application/x-www-form-urlencoded (default);POST method and setting the enctype attribute to text/plain;POST method and setting the enctype attribute to multipart/form-data;GET method (in this case the enctype attribute will be ignored).Now, consider the submission of a form containing only two fields, named foo and baz. If you are using the POST method the server will receive a string similar to one of the following three examples, depending on the encoding type you are using:
Method: POST; Encoding type: application/x-www-form-urlencoded (default):
Content-Type: application/x-www-form-urlencoded foo=bar&baz=The+first+line.%0D%0AThe+second+line.%0D%0A
Method: POST; Encoding type: text/plain:
Content-Type: text/plain foo=bar baz=The first line. The second line.
Method: POST; Encoding type: multipart/form-data:
Content-Type: multipart/form-data; boundary=---------------------------314911788813839 -----------------------------314911788813839 Content-Disposition: form-data; name="foo" bar -----------------------------314911788813839 Content-Disposition: form-data; name="baz" The first line. The second line. -----------------------------314911788813839--
However, if you are using the GET method, a string like the following will be simply added to the URL:
?foo=bar&baz=The%20first%20line.%0AThe%20second%20line.
All these effects are done automatically by the web browser whenever you submit a {{HTMLElement("form")}}. If you want to perform the same effects using JavaScript you have to instruct the interpreter about everything. Therefore, how to send forms in pure AJAX is too complex to be explained here in detail. For this reason, here we place a complete (yet didactic) framework, able to use all four ways to submit, and to upload files:
<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Sending forms with pure AJAX – MDN</title>
<script type="text/javascript">
"use strict";
/*\
|*|
|*| :: XMLHttpRequest.prototype.sendAsBinary() Polyfill ::
|*|
|*| https://developer.mozilla.org/en-US/docs/DOM/XMLHttpRequest#sendAsBinary()
\*/
if (!XMLHttpRequest.prototype.sendAsBinary) {
XMLHttpRequest.prototype.sendAsBinary = function(sData) {
var nBytes = sData.length, ui8Data = new Uint8Array(nBytes);
for (var nIdx = 0; nIdx < nBytes; nIdx++) {
ui8Data[nIdx] = sData.charCodeAt(nIdx) & 0xff;
}
/* send as ArrayBufferView...: */
this.send(ui8Data);
/* ...or as ArrayBuffer (legacy)...: this.send(ui8Data.buffer); */
};
}
/*\
|*|
|*| :: AJAX Form Submit Framework ::
|*|
|*| https://developer.mozilla.org/en-US/docs/DOM/XMLHttpRequest/Using_XMLHttpRequest
|*|
|*| This framework is released under the GNU Public License, version 3 or later.
|*| https://www.gnu.org/licenses/gpl-3.0-standalone.html
|*|
|*| Syntax:
|*|
|*| AJAXSubmit(HTMLFormElement);
\*/
var AJAXSubmit = (function () {
function ajaxSuccess () {
/* console.log("AJAXSubmit - Success!"); */
console.log(this.responseText);
/* you can get the serialized data through the "submittedData" custom property: */
/* console.log(JSON.stringify(this.submittedData)); */
}
function submitData (oData) {
/* the AJAX request... */
var oAjaxReq = new XMLHttpRequest();
oAjaxReq.submittedData = oData;
oAjaxReq.onload = ajaxSuccess;
if (oData.technique === 0) {
/* method is GET */
oAjaxReq.open("get", oData.receiver.replace(/(?:\?.*)?$/,
oData.segments.length > 0 ? "?" + oData.segments.join("&") : ""), true);
oAjaxReq.send(null);
} else {
/* method is POST */
oAjaxReq.open("post", oData.receiver, true);
if (oData.technique === 3) {
/* enctype is multipart/form-data */
var sBoundary = "---------------------------" + Date.now().toString(16);
oAjaxReq.setRequestHeader("Content-Type", "multipart\/form-data; boundary=" + sBoundary);
oAjaxReq.sendAsBinary("--" + sBoundary + "\r\n" +
oData.segments.join("--" + sBoundary + "\r\n") + "--" + sBoundary + "--\r\n");
} else {
/* enctype is application/x-www-form-urlencoded or text/plain */
oAjaxReq.setRequestHeader("Content-Type", oData.contentType);
oAjaxReq.send(oData.segments.join(oData.technique === 2 ? "\r\n" : "&"));
}
}
}
function processStatus (oData) {
if (oData.status > 0) { return; }
/* the form is now totally serialized! do something before sending it to the server... */
/* doSomething(oData); */
/* console.log("AJAXSubmit - The form is now serialized. Submitting..."); */
submitData (oData);
}
function pushSegment (oFREvt) {
this.owner.segments[this.segmentIdx] += oFREvt.target.result + "\r\n";
this.owner.status--;
processStatus(this.owner);
}
function plainEscape (sText) {
/* How should I treat a text/plain form encoding?
What characters are not allowed? this is what I suppose...: */
/* "4\3\7 - Einstein said E=mc2" ----> "4\\3\\7\ -\ Einstein\ said\ E\=mc2" */
return sText.replace(/[\s\=\\]/g, "\\$&");
}
function SubmitRequest (oTarget) {
var nFile, sFieldType, oField, oSegmReq, oFile, bIsPost = oTarget.method.toLowerCase() === "post";
/* console.log("AJAXSubmit - Serializing form..."); */
this.contentType = bIsPost && oTarget.enctype ? oTarget.enctype : "application\/x-www-form-urlencoded";
this.technique = bIsPost ?
this.contentType === "multipart\/form-data" ? 3 : this.contentType === "text\/plain" ? 2 : 1 : 0;
this.receiver = oTarget.action;
this.status = 0;
this.segments = [];
var fFilter = this.technique === 2 ? plainEscape : escape;
for (var nItem = 0; nItem < oTarget.elements.length; nItem++) {
oField = oTarget.elements[nItem];
if (!oField.hasAttribute("name")) { continue; }
sFieldType = oField.nodeName.toUpperCase() === "INPUT" ? oField.getAttribute("type").toUpperCase() : "TEXT";
if (sFieldType === "FILE" && oField.files.length > 0) {
if (this.technique === 3) {
/* enctype is multipart/form-data */
for (nFile = 0; nFile < oField.files.length; nFile++) {
oFile = oField.files[nFile];
oSegmReq = new FileReader();
/* (custom properties:) */
oSegmReq.segmentIdx = this.segments.length;
oSegmReq.owner = this;
/* (end of custom properties) */
oSegmReq.onload = pushSegment;
this.segments.push("Content-Disposition: form-data; name=\"" +
oField.name + "\"; filename=\"" + oFile.name +
"\"\r\nContent-Type: " + oFile.type + "\r\n\r\n");
this.status++;
oSegmReq.readAsBinaryString(oFile);
}
} else {
/* enctype is application/x-www-form-urlencoded or text/plain or
method is GET: files will not be sent! */
for (nFile = 0; nFile < oField.files.length;
this.segments.push(fFilter(oField.name) + "=" + fFilter(oField.files[nFile++].name)));
}
} else if ((sFieldType !== "RADIO" && sFieldType !== "CHECKBOX") || oField.checked) {
/* NOTE: this will submit _all_ submit buttons. Detecting the correct one is non-trivial. */
/* field type is not FILE or is FILE but is empty */
this.segments.push(
this.technique === 3 ? /* enctype is multipart/form-data */
"Content-Disposition: form-data; name=\"" + oField.name + "\"\r\n\r\n" + oField.value + "\r\n"
: /* enctype is application/x-www-form-urlencoded or text/plain or method is GET */
fFilter(oField.name) + "=" + fFilter(oField.value)
);
}
}
processStatus(this);
}
return function (oFormElement) {
if (!oFormElement.action) { return; }
new SubmitRequest(oFormElement);
};
})();
</script>
</head>
<body>
<h1>Sending forms with pure AJAX</h1>
<h2>Using the GET method</h2>
<form action="register.php" method="get" onsubmit="AJAXSubmit(this); return false;">
<fieldset>
<legend>Registration example</legend>
<p>
First name: <input type="text" name="firstname" /><br />
Last name: <input type="text" name="lastname" />
</p>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
</form>
<h2>Using the POST method</h2>
<h3>Enctype: application/x-www-form-urlencoded (default)</h3>
<form action="register.php" method="post" onsubmit="AJAXSubmit(this); return false;">
<fieldset>
<legend>Registration example</legend>
<p>
First name: <input type="text" name="firstname" /><br />
Last name: <input type="text" name="lastname" />
</p>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
</form>
<h3>Enctype: text/plain</h3>
<form action="register.php" method="post" enctype="text/plain"
onsubmit="AJAXSubmit(this); return false;">
<fieldset>
<legend>Registration example</legend>
<p>
Your name: <input type="text" name="user" />
</p>
<p>
Your message:<br />
<textarea name="message" cols="40" rows="8"></textarea>
</p>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
</form>
<h3>Enctype: multipart/form-data</h3>
<form action="register.php" method="post" enctype="multipart/form-data"
onsubmit="AJAXSubmit(this); return false;">
<fieldset>
<legend>Upload example</legend>
<p>
First name: <input type="text" name="firstname" /><br />
Last name: <input type="text" name="lastname" /><br />
Sex:
<input id="sex_male" type="radio" name="sex" value="male" />
<label for="sex_male">Male</label>
<input id="sex_female" type="radio" name="sex" value="female" />
<label for="sex_female">Female</label><br />
Password: <input type="password" name="secret" /><br />
What do you prefer:
<select name="image_type">
<option>Books</option>
<option>Cinema</option>
<option>TV</option>
</select>
</p>
<p>
Post your photos:
<input type="file" multiple name="photos[]">
</p>
<p>
<input id="vehicle_bike" type="checkbox" name="vehicle[]" value="Bike" />
<label for="vehicle_bike">I have a bike</label><br />
<input id="vehicle_car" type="checkbox" name="vehicle[]" value="Car" />
<label for="vehicle_car">I have a car</label>
</p>
<p>
Describe yourself:<br />
<textarea name="description" cols="50" rows="8"></textarea>
</p>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
</form>
</body>
</html>
To test this, create a page named register.php (which is the action attribute of these sample forms), and put the following minimalistic content:
<?php
/* register.php */
header("Content-type: text/plain");
/*
NOTE: You should never use `print_r()` in production scripts, or
otherwise output client-submitted data without sanitizing it first.
Failing to sanitize can lead to cross-site scripting vulnerabilities.
*/
echo ":: data received via GET ::\n\n";
print_r($_GET);
echo "\n\n:: Data received via POST ::\n\n";
print_r($_POST);
echo "\n\n:: Data received as \"raw\" (text/plain encoding) ::\n\n";
if (isset($HTTP_RAW_POST_DATA)) { echo $HTTP_RAW_POST_DATA; }
echo "\n\n:: Files received ::\n\n";
print_r($_FILES);
The syntax to activate this script is simply:
AJAXSubmit(myForm);
FileReader API. But, since the aim of this script is to work with a stringifiable raw data, we used the {{domxref("XMLHttpRequest.sendAsBinary()", "sendAsBinary()")}} method in conjunction with the {{domxref("FileReader.readAsBinaryString()", "readAsBinaryString()")}} method of the FileReader API. As such, the above script makes sense only when you are dealing with small files. If you do not intend to upload binary content, consider instead using the FormData API.sendAsBinary method is considered deprecated as of Gecko 31 {{geckoRelease(31)}} and will be removed soon. The standard send(Blob data) method can be used instead.The {{domxref("XMLHttpRequest.FormData", "FormData")}} constructor lets you compile a set of key/value pairs to send using XMLHttpRequest. Its primary use is in sending form data, but can also be used independently from a form in order to transmit user keyed data. The transmitted data is in the same format the form's submit() method uses to send data, if the form's encoding type were set to "multipart/form-data". FormData objects can be utilized in a number of ways with an XMLHttpRequest. For examples, and explanations of how one can utilize FormData with XMLHttpRequests, see the Using FormData Objects page. For didactic purposes here is a translation of the previous example transformed to use the FormData API. Note the brevity of the code:
<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" charset="UTF-8" />
<title>Sending forms with FormData – MDN</title>
<script>
"use strict";
function ajaxSuccess () {
console.log(this.responseText);
}
function AJAXSubmit (oFormElement) {
if (!oFormElement.action) { return; }
var oReq = new XMLHttpRequest();
oReq.onload = ajaxSuccess;
if (oFormElement.method.toLowerCase() === "post") {
oReq.open("post", oFormElement.action);
oReq.send(new FormData(oFormElement));
} else {
var oField, sFieldType, nFile, sSearch = "";
for (var nItem = 0; nItem < oFormElement.elements.length; nItem++) {
oField = oFormElement.elements[nItem];
if (!oField.hasAttribute("name")) { continue; }
sFieldType = oField.nodeName.toUpperCase() === "INPUT" ?
oField.getAttribute("type").toUpperCase() : "TEXT";
if (sFieldType === "FILE") {
for (nFile = 0; nFile < oField.files.length;
sSearch += "&" + escape(oField.name) + "=" + escape(oField.files[nFile++].name));
} else if ((sFieldType !== "RADIO" && sFieldType !== "CHECKBOX") || oField.checked) {
sSearch += "&" + escape(oField.name) + "=" + escape(oField.value);
}
}
oReq.open("get", oFormElement.action.replace(/(?:\?.*)?$/, sSearch.replace(/^&/, "?")), true);
oReq.send(null);
}
}
</script>
</head>
<body>
<h1>Sending forms with FormData</h1>
<h2>Using the GET method</h2>
<form action="register.php" method="get" onsubmit="AJAXSubmit(this); return false;">
<fieldset>
<legend>Registration example</legend>
<p>
First name: <input type="text" name="firstname" /><br />
Last name: <input type="text" name="lastname" />
</p>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
</form>
<h2>Using the POST method</h2>
<h3>Enctype: application/x-www-form-urlencoded (default)</h3>
<form action="register.php" method="post" onsubmit="AJAXSubmit(this); return false;">
<fieldset>
<legend>Registration example</legend>
<p>
First name: <input type="text" name="firstname" /><br />
Last name: <input type="text" name="lastname" />
</p>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
</form>
<h3>Enctype: text/plain</h3>
<p>The text/plain encoding is not supported by the FormData API.</p>
<h3>Enctype: multipart/form-data</h3>
<form action="register.php" method="post" enctype="multipart/form-data"
onsubmit="AJAXSubmit(this); return false;">
<fieldset>
<legend>Upload example</legend>
<p>
First name: <input type="text" name="firstname" /><br />
Last name: <input type="text" name="lastname" /><br />
Sex:
<input id="sex_male" type="radio" name="sex" value="male" />
<label for="sex_male">Male</label>
<input id="sex_female" type="radio" name="sex" value="female" />
<label for="sex_female">Female</label><br />
Password: <input type="password" name="secret" /><br />
What do you prefer:
<select name="image_type">
<option>Books</option>
<option>Cinema</option>
<option>TV</option>
</select>
</p>
<p>
Post your photos:
<input type="file" multiple name="photos[]">
</p>
<p>
<input id="vehicle_bike" type="checkbox" name="vehicle[]" value="Bike" />
<label for="vehicle_bike">I have a bike</label><br />
<input id="vehicle_car" type="checkbox" name="vehicle[]" value="Car" />
<label for="vehicle_car">I have a car</label>
</p>
<p>
Describe yourself:<br />
<textarea name="description" cols="50" rows="8"></textarea>
</p>
<p>
<input type="submit" value="Submit" />
</p>
</fieldset>
</form>
</body>
</html>
file {{ HTMLElement("input") }} fields, when you submit a form through the FormData API you do not need to use the {{domxref("FileReader")}} API also: files are automatically loaded and uploaded.function getHeaderTime () {
console.log(this.getResponseHeader("Last-Modified")); /* A valid GMTString date or null */
}
var oReq = new XMLHttpRequest();
oReq.open("HEAD" /* use HEAD if you only need the headers! */, "yourpage.html");
oReq.onload = getHeaderTime;
oReq.send();
Let's create two functions:
function getHeaderTime () {
var nLastVisit = parseFloat(window.localStorage.getItem('lm_' + this.filepath));
var nLastModif = Date.parse(this.getResponseHeader("Last-Modified"));
if (isNaN(nLastVisit) || nLastModif > nLastVisit) {
window.localStorage.setItem('lm_' + this.filepath, Date.now());
isFinite(nLastVisit) && this.callback(nLastModif, nLastVisit);
}
}
function ifHasChanged(sURL, fCallback) {
var oReq = new XMLHttpRequest();
oReq.open("HEAD" /* use HEAD - we only need the headers! */, sURL);
oReq.callback = fCallback;
oReq.filepath = sURL;
oReq.onload = getHeaderTime;
oReq.send();
}
And to test:
/* Let's test the file "yourpage.html"... */
ifHasChanged("yourpage.html", function (nModif, nVisit) {
console.log("The page '" + this.filepath + "' has been changed on " + (new Date(nModif)).toLocaleString() + "!");
});
If you want to know if the current page has changed, please read the article about {{domxref("document.lastModified")}}.
Modern browsers support cross-site requests by implementing the Cross-Origin Resource Sharing (CORS) standard. As long as the server is configured to allow requests from your web application's origin, XMLHttpRequest will work. Otherwise, an INVALID_ACCESS_ERR exception is thrown.
A cross-browser compatible approach to bypassing the cache is appending a timestamp to the URL, being sure to include a "?" or "&" as appropriate. For example:
http://foo.com/bar.html -> http://foo.com/bar.html?12345 http://foo.com/bar.html?foobar=baz -> http://foo.com/bar.html?foobar=baz&12345
As the local cache is indexed by URL, this causes every request to be unique, thereby bypassing the cache.
You can automatically adjust URLs using the following code:
var oReq = new XMLHttpRequest();
oReq.open("GET", url + ((/\?/).test(url) ? "&" : "?") + (new Date()).getTime());
oReq.send(null);
{{fx_minversion_note(3, "Versions of Firefox prior to Firefox 3 allowed you to set the preference capability.policy.<policyname>.XMLHttpRequest.open</policyname> to allAccess to give specific sites cross-site access. This is no longer supported.")}}
{{fx_minversion_note(5, "Versions of Firefox prior to Firefox 5 could use netscape.security.PrivilegeManager.enablePrivilege(\"UniversalBrowserRead\"); to request cross-site access. This is no longer supported, even though it produces no warning and permission dialog is still presented.")}}
The recommended way to enable cross-site scripting is to use the Access-Control-Allow-Origin HTTP header in the response to the XMLHttpRequest.
If you conclude with an XMLHttpRequest receiving status=0 and statusText=null, this means the request was not allowed to be performed. It was UNSENT. A likely cause for this is when the XMLHttpRequest origin (at the creation of the XMLHttpRequest) has changed when the XMLHttpRequest is subsequently open(). This case can happen, for example, when one has an XMLHttpRequest that gets fired on an onunload event for a window, the expected XMLHttpRequest is created when the window to be closed is still there, and finally sending the request (in otherwords, open()) when this window has lost its focus and another window gains focus. The most effective way to avoid this problem is to set a listener on the new window's {{event("activate")}} event which is set once the terminated window has its {{event("unload")}} event triggered.
Setting overrideMimeType does not work from a {{domxref("Worker")}}. See {{bug(678057)}} for more details. Other browsers may handle this differently.
| Specification | Status | Comment |
|---|---|---|
| {{SpecName('XMLHttpRequest')}} | {{Spec2('XMLHttpRequest')}} | Live standard, latest version |
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
{{Compat("api.XMLHttpRequest")}}