responseType
property of the XMLHttpRequest object can be set to change the expected response type from the server. Possible values are the empty string (default),
"arraybuffer"
,
"blob"
,
"document"
,
"json"
，和
"text"
。
response
property will contain the entity body according to
responseType
, as an
ArrayBuffer
,
Blob
,
Document
,
JSON
, or string. This is
null
if the request is not complete or was not successful.
This example reads an image as a binary file and creates an 8-bit unsigned integer array from the raw bytes. Note that this will not decode the image and read the pixels. You will need a png decoding library 为此。
var oReq = new XMLHttpRequest();
oReq.open("GET", "/myfile.png", true);
oReq.responseType = "arraybuffer";
oReq.onload = function (oEvent) {
var arrayBuffer = oReq.response; // Note: not oReq.responseText
if (arrayBuffer) {
var byteArray = new Uint8Array(arrayBuffer);
for (var i = 0; i < byteArray.byteLength; i++) {
// do something with each byte in the array
}
}
};
oReq.send(null);
You can also read a binary file as a
Blob
by setting the string
"blob"
到
responseType
特性。
var oReq = new XMLHttpRequest();
oReq.open("GET", "/myfile.png", true);
oReq.responseType = "blob";
oReq.onload = function(oEvent) {
var blob = oReq.response;
// ...
};
oReq.send();
load_binary_resource()
function shown below loads binary data from the specified URL, returning it to the caller.
function load_binary_resource(url) {
var req = new XMLHttpRequest();
req.open('GET', url, false);
//XHR binary charset opt by Marcus Granado 2006 [http://mgran.blogspot.com]
req.overrideMimeType('text\/plain; charset=x-user-defined');
req.send(null);
if (req.status != 200) return '';
return req.responseText;
}
The magic happens in line 5, which overrides the MIME type, forcing the browser to treat it as plain text, using a user-defined character set. This tells the browser not to parse it, and to let the bytes pass through unprocessed.
var filestream = load_binary_resource(url); var abyte = filestream.charCodeAt(x) & 0xff; // throw away high-order byte (f7)
The example above fetches the byte at offset
x
within the loaded binary data. The valid range for
x
is from 0 to
filestream.length-1
.
见 downloading binary streams with XMLHttpRequest for a detailed explanation. See also downloading files .
send
method of the XMLHttpRequest has been extended to enable easy transmission of binary data by accepting an
ArrayBuffer
,
Blob
，或
File
对象。
The following example creates a text file on-the-fly and uses the
POST
method to send the "file" to the server. This example uses plain text, but you can imagine the data being a binary file instead.
var oReq = new XMLHttpRequest();
oReq.open("POST", url, true);
oReq.onload = function (oEvent) {
// Uploaded.
};
var blob = new Blob(['abc123'], {type: 'text/plain'});
oReq.send(blob);
You can send JavaScript typed arrays as binary data as well.
var myArray = new ArrayBuffer(512);
var longInt8View = new Uint8Array(myArray);
// generate some data
for (var i=0; i< longInt8View.length; i++) {
longInt8View[i] = i % 256;
}
var xhr = new XMLHttpRequest;
xhr.open("POST", url, false);
xhr.send(myArray);
This is building a 512-byte array of 8-bit integers and sending it; you can use any binary data you'd like, of course.
注意： Support for sending
ArrayBuffer
objects using XMLHttpRequest was added to Gecko 9.0 (Firefox 9.0 / Thunderbird 9.0 / SeaMonkey 2.6).
Add information about other browsers' support here.
Please, read this paragraph .
This example transmits binary content asynchronously, using the
POST
method, and Firefox's non-standard
sendAsBinary()
.
var req = new XMLHttpRequest();
req.open("POST", url, true);
// set headers and mime-type appropriately
req.setRequestHeader("Content-Length", 741);
req.sendAsBinary(aBody);
Line 4 sets the Content-Length header to 741, indicating that the data is 741 bytes long. Obviously you need to change this value based on the actual size of the data being sent.
Line 5 uses the
sendAsBinary()
method to initiate the request.
sendAsBinary
method is considered deprecated as of Gecko 31 (Firefox 31 / Thunderbird 31 / SeaMonkey 2.28) and will be removed soon. The standard
send(Blob data)
method can be used instead as explained above.
You can also send binary content by passing an instance of the
nsIFileInputStream
to
send()
. In that case, you don't have to set the
Content-Length
header yourself, as the information is fetched from the stream automatically:
// Make a stream from a file.
var stream = Components.classes["@mozilla.org/network/file-input-stream;1"]
.createInstance(Components.interfaces.nsIFileInputStream);
stream.init(file, 0x04 | 0x08, 0644, 0x04); // file is an nsIFile instance
// Try to determine the MIME type of the file
var mimeType = "text\/plain";
try {
var mimeService = Components.classes["@mozilla.org/mime;1"]
.getService(Components.interfaces.nsIMIMEService);
mimeType = mimeService.getTypeFromFile(file); // file is an nsIFile instance
}
catch (oEvent) { /* eat it; just use text/plain */ }
// Send
var req = Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"]
.createInstance(Components.interfaces.nsIXMLHttpRequest);
req.open('PUT', url, false); /* synchronous! */
req.setRequestHeader('Content-Type', mimeType);
req.send(stream);
XMLHttpRequest