XMLHttpRequest.responseType - Web APIs 编辑

The XMLHttpRequest property responseType is an enumerated string value specifying the type of data contained in the response. It also lets the author change the response type. If an empty string is set as the value of responseType, the default value of text is used.

Syntax

var type = XMLHttpRequest.responseType;

XMLHttpRequest.responseType = type;

Value

A string taken from the XMLHttpRequestResponseType enum which specifies what type of data the response contains.

When setting responseType to a particular value, the author should make sure that the server is actually sending a response compatible with that format. If the server returns data that is not compatible with the responseType that was set, the value of response will be null.

The values supported by responseType are the following:

""

An empty responseType string is treated the same as "text", the default type.

arraybuffer

The response is a JavaScript ArrayBuffer containing binary data.

blob

The response is a Blob object containing the binary data.

document

The response is an HTML Document or XML XMLDocument, as appropriate based on the MIME type of the received data. See HTML in XMLHttpRequest to learn more about using XHR to fetch HTML content.

json

The response is a JavaScript object created by parsing the contents of received data as JSON.

text

The response is a text in a DOMString object.

ms-stream

The response is part of a streaming download; this response type is only allowed for download requests, and is only supported by Internet Explorer.

Exceptions

InvalidAccessError

An attempt was made to change the value of responseType on anXMLHttpRequest which is in synchronous mode but not in a Worker. For additional details, see Synchronous XHR restrictions below.

Usage notes

Synchronous XHR restrictions

You cannot change the value of responseType in a synchronous XMLHttpRequest except when the request belongs to a Worker. This restriction is designed in part to help ensure that synchronous operations aren't used for large transactions that block the browser's main thread, thereby bogging down the user experience.

XMLHttpRequests are asynchronous by default; they are only placed in synchronous mode by passing false as the value of the optional async parameter when calling open().

Restrictions in Workers

Attempts to set the value of responseType to document are ignored in a Worker.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Using XMLHttpRequest
• HTML in XMLHttpRequest
• The response data: response, responseText, and responseXML