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XMLHttpRequest.send() 方法用于发送 HTTP 请求。如果是异步请求(默认为异步请求),则此方法会在请求发送后立即返回;如果是同步请求,则此方法直到响应到达后才会返回。XMLHttpRequest.send() 方法接受一个可选的参数,其作为请求主体;如果请求方法是 GET 或者 HEAD,则应将请求主体设置为 null。

If no Accept header has been set using the setRequestHeader(), an Accept header with the */* is sent.

Note: Be aware to stop using a plain ArrayBuffer as parameter. This is not part of the XMLHttpRequest specification any longer. Use an ArrayBufferView instead (see compatibility table for version information).


void send();
void send(ArrayBuffer data);
void send(ArrayBufferView data);
void send(Blob data);
void send(Document data);
void send(DOMString? data);
void send(FormData data);

If the data is a Document, it is serialized before being sent. When sending a Document, versions of Firefox prior to version 3 always sends the request using UTF-8 encoding; Firefox 3 properly sends the document using the encoding specified by body.xmlEncoding, or UTF-8 if no encoding is specified.

If it's an nsIInputStream, it must be compatible with nsIUploadChannel's setUploadStream()method. In that case, a Content-Length header is added to the request, with its value obtained using nsIInputStream's available()method. Any headers included at the top of the stream are treated as part of the message body. The stream's MIMEtype should be specified by setting the Content-Type header using the setRequestHeader() method prior to calling send().

The best way to send binary content (like in files upload) is using an ArrayBufferView or Blobs in conjuncton with the send() method.

Example: GET

var xhr = new XMLHttpRequest();'GET', '/server', true);

xhr.onload = function () {
  // Request finished. Do processing here.

// xhr.send('string');
// xhr.send(new Blob());
// xhr.send(new Int8Array());
// xhr.send({ form: 'data' });
// xhr.send(document);


Example: POST

var xhr = new XMLHttpRequest();"POST", '/server', true);

//Send the proper header information along with the request
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

xhr.onreadystatechange = function() {//Call a function when the state changes.
    if(xhr.readyState == XMLHttpRequest.DONE && xhr.status == 200) {
        // Request finished. Do processing here.
// xhr.send('string'); 
// xhr.send(new Blob()); 
// xhr.send(new Int8Array()); 
// xhr.send({ form: 'data' }); 
// xhr.send(document);



Specification Status Comment
Living Standard WHATWG living standard

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 1 1.0 (1.7 or earlier) 5[2]
(Yes) 1.2
send(ArrayBuffer) 9 9.0 (9.0)[1] 10 11.60 ?
send(ArrayBufferView) 22 20.0 (20.0) ? ? ?
send(Blob) 7 3.6 (1.9.2) 10 12 ?
send(FormData) 6 4.0 (2.0) 10 12 ?
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? 1.0 (Yes) ? ? ?
send(ArrayBuffer) ? ? ? ? ?
send(ArrayBufferView) ? ? ? ? ?
send(Blob) ? ? ? ? ?
send(FormData) ? ? ? ? ?

[1] Sending a plain ArrayBuffer is not part of the XMLHttpRequest specification any longer and should be treated as deprecated. Use  ArrayBufferView instead, which was added to Gecko version 20.0 (Firefox 20.0 / Thunderbird 20.0 / SeaMonkey 2.17).

[2] This feature was implemented via ActiveXObject(). Since version 7 Internet Explorer implements the standard XMLHttpRequest.


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