GM xmlhttpRequest

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The correct title of this article is GM_xmlhttpRequest. The substitution or omission of an _ is due to technical restrictions.



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[edit] Description

This API method provides access to the chrome-privileged XMLHttpRequest object. This means that it is possible to issue requests to domains other than that of the current page.

Additional reference may be found at:

Examples | Notes

[edit] Syntax

GM_xmlhttpRequest( details )

Value: Function
Returns: undefined, response Object
Compatibility: Greasemonkey 0.2.5+
details Object
Properties Event Handler Callbacks
method onload
url onreadystatechange
headers onerror
overrideMimeType
data
  • All properties and event handler callbacks are optional except method and url.

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[edit] Properties

[edit] method

Value: String
Usage: details.method = "GET"';

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[edit] url

Value: String
Usage: details.url = "http://www.greasespot.net/";
  • Must be an absolute URL.

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[edit] headers

Value: Object
Usage: details.headers = {"User-Agent":"Mozilla/5.0"};
  • The headers property is an object which is typically used to override the default browser generated headers, also known as atoms. It should contain the atom-value pairs of the headers to send.[2]

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[edit] overrideMimeType

Value: String
Compatibility: Greasemonkey 0.6.8+
Usage: details.overrideMimeType = "text/html; charset=ISO-8859-1";
  • While each character set name may have multiple aliases defined, there may be a preferred name which can be found at IANA

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[edit] data

Value: String
Usage: details.data = null; /* some code */ if (details.data) { /* some code */ }
  • [1]
  • Note that if the data field contains form-encoded data, you must also set the header 'Content-Type': 'application/x-www-form-urlencoded' in the headers field.

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[edit] Event Handler Callbacks

[edit] onload

Usage: details.onload = function (response) { /* some code */ };
Returns: undefined, response Object

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[edit] onreadystatechange

Usage: details.onreadystatechange = function (response) { /* some code */ };
Returns: undefined, response Object

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[edit] onerror

Usage: details.onerror = function (response) { /* some code */ };
Returns: undefined, response Object

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response Object
Properties
status readyState responseText finalUrl
statusText responseHeaders
  • Note: there is no responseXML property, contrary to what people used to XMLHttpRequest might expect. This is due to security restrictions imposed on the XMLDocument created in the privileged GM core context. One can easily create its own XMLDocument out of responseText using a DOMParser (see examples below).

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[edit] Properties

[edit] status

Value: Number
Usage: if (response.status == 200) { /* some code */ }

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[edit] statusText

Value: String
Usage: if (response.statusText == "OK") { /* some code */ }

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[edit] readyState

Value: Number
Usage: if (response.readyState == 4) { /* some code */ }

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[edit] responseText

Value: String
Usage: alert(response.responseText);

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[edit] responseHeaders

Value: String
Usage: if (response.responseHeaders) { /* some code */ }
  • The responseHeaders is the string representation of response headers returned by XMLHTTPRequest.getAllResponseHeaders().

[edit] finalUrl

Value: String
Compatibility: Greasemonkey 0.8.0+
Usage: if (response.finalUrl) { /* some code */ }

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[edit] Examples 

GM_xmlhttpRequest({
  method: "GET",
  url: "http://www.example.net/",
  headers: {
    "User-Agent": "Mozilla/5.0",            // Recommend using navigator.userAgent when possible
    "Accept": "text/xml"
  },
  onload: function(response) {
    // Inject responseXML into existing Object if not present
    if (!response.responseXML)
      response.responseXML = new DOMParser().parseFromString(response.responseText, "text/xml");

    GM_log([
      response.status,
      response.statusText,
      response.readyState,
      response.responseHeaders,
      response.responseText,
      response.finalUrl,
      response.responseXML
    ].join("\n"));
  }
});


When making a POST request, some sites require the Content-Type header to be included as such: 

GM_xmlhttpRequest({
  method: "POST",
  url: "http://www.example.net/login",
  data: "username=johndoe&password=xyz123",
  headers: {
    "Content-Type": "application/x-www-form-urlencoded"
  },
  onload: function(response) {
     if (response.responseText.indexOf("Logged in as") > -1)
       location.href = "http://www.example.net/dashboard";
  }
});
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[edit] Notes

[1]Some users have reported problems with international character sets. See these mailing list threads

Resolved: Greasemonkey exposed the overrideMimeType method to allow changing of the desired charset.

[2]Some header atoms may not actually work through GM_xmlhttpRequest. The Referer atom is one that is known to be recognized but appears to be content filtered by the browser. This may be due to security restrictions to keep user scripts from doing unsafe things.

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Retrieved from "http://wiki.greasespot.net/GM_xmlhttpRequest"
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