small xhr abstraction

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102.6.02 years ago4 years agoMinified + gzip package size for @videojs/xhr in KB


Originally forked from naugtur/xhr.

A small XMLHttpRequest wrapper. Designed for use with browserify, webpack etc.
API is a subset of request so you can write code that works in both node.js and the browser by using require('request') in your code and telling your browser bundler to load xhr instead of request.
For browserify, add a browser field to your package.json:
"browser": {
  "request": "@videojs/xhr"

For webpack, add a resolve.alias field to your configuration:
"resolve": {
  "alias": {
    "request$": "@videojs/xhr"

Browser support: IE8+ and everything else.


npm install @videojs/xhr


var xhr = require("@videojs/xhr")

    method: "post",
    body: someJSONString,
    uri: "/foo",
    headers: {
        "Content-Type": "application/json"
}, function (err, resp, body) {
    // check resp.statusCode

var req = xhr(options, callback)

type XhrOptions = String | {
    useXDR: Boolean?,
    sync: Boolean?,
    uri: String,
    url: String,
    method: String?,
    timeout: Number?,
    headers: Object?,
    body: String? | Object?,
    json: Boolean? | Object?,
    username: String?,
    password: String?,
    withCredentials: Boolean?,
    responseType: String?,
    beforeSend: Function?
xhr := (XhrOptions, Callback<Response>) => Request
the returned object is either an XMLHttpRequest3 instance
or an [`XDomainRequest`][4] instance (if on IE8/IE9 &&
`options.useXDR` is set to `true`)


Your callback will be called once with the arguments
( [`Error`][5], `response` , `body` ) where the response is an object:
    body: Object||String,
    statusCode: Number,
    method: String,
    headers: {},
    url: String,
    rawRequest: xhr
- body: HTTP response body - XMLHttpRequest.response6, XMLHttpRequest.responseText7 or
[`XMLHttpRequest.responseXML`][8] depending on the request type.
- rawRequest: Original XMLHttpRequest3 instance
or [`XDomainRequest`][4] instance (if on IE8/IE9 &&
`options.useXDR` is set to `true`)
- headers: A collection of headers where keys are header names converted to lowercase
Your callback will be called with an Error5 if there is an error in the browser that prevents sending the request. A HTTP 500 response is not going to cause an error to be returned.

Other signatures

  • var req = xhr(url, callback) -
a simple string instead of the options. In this case, a GET request will be made to that url.
  • var req = xhr(url, options, callback) -
the above may also be called with the standard set of options.

Convience methods

  • var req = xhr.{post, put, patch, del, head, get}(url, callback)
  • var req = xhr.{post, put, patch, del, head, get}(options, callback)
  • var req = xhr.{post, put, patch, del, head, get}(url, options, callback)

The xhr module has convience functions attached that will make requests with the given method. Each function is named after its method, with the exception of DELETE which is called xhr.del for compatibility.
The method shorthands may be combined with the url-first form of xhr for succinct and descriptive requests. For example,
xhr.post('/post-to-me', function(err, resp) {

xhr.del('/delete-me', { headers: { my: 'auth' } }, function (err, resp) {



Specify the method the XMLHttpRequest3 should be opened
with. Passed to [`XMLHttpRequest.open`][2]. Defaults to "GET"


Specify whether this is a cross origin (CORS) request for IE<10.
Switches IE to use [`XDomainRequest`][4] instead of `XMLHttpRequest`.
Ignored in other browsers.
Note that headers cannot be set on an XDomainRequest instance.


Specify whether this is a synchrounous request. Note that when
this is true the callback will be called synchronously. In
most cases this option should not be used. Only use if you
know what you are doing!


Pass in body to be send across the XMLHttpRequest3.
Generally should be a string. But anything that's valid as
a parameter to [`XMLHttpRequest.send`][1] should work  (Buffer for file, etc.).
If options.json is true, then this must be a JSON-serializable object. options.body is passed to JSON.stringify and sent.

options.uri or options.url

The uri to send a request to. Passed to XMLHttpRequest.open2. options.url and options.uri are aliases for each other.


An object of headers that should be set on the request. The
key, value pair is passed to [`XMLHttpRequest.setRequestHeader`][9]


Number of miliseconds to wait for response. Defaults to 0 (no timeout). Ignored when options.sync is true.


Set to true to send request as application/json (see options.body) and parse response from JSON.
For backwards compatibility options.json can also be a valid JSON-serializable value to be sent to the server. Additionally the response body is still parsed as JSON
For sending booleans as JSON body see FAQ


Specify whether user credentials are to be included in a cross-origin
request. Sets [`XMLHttpRequest.withCredentials`][10]. Defaults to false.
A wildcard * cannot be used in the Access-Control-Allow-Origin header when withCredentials is true.
The header needs to specify your origin explicitly or browser will abort the request.


Determines the data type of the response. Sets XMLHttpRequest.responseType11. For example, a responseType of document will return a parsed Document object as the response.body for an XML resource.


A function being called right before the send method of the XMLHttpRequest or XDomainRequest instance is called. The XMLHttpRequest or XDomainRequest instance is passed as an argument.


Pass an XMLHttpRequest object (or something that acts like one) to use instead of constructing a new one using the XMLHttpRequest or XDomainRequest constructors. Useful for testing.


This module exposes the following helpers on the xhr object.

xhr.httpHandler(callback, decodeResponseBody) => XhrCallback

httpHandler is a wrapper for the XhrCallback which returns an error for HTTP Status Codes 4xx and 5xx. Given a callback, it'll either return an error with the response body as the error's cause, or return the response body.
Usage like so:
    uri: "https://example.com/foo",
    responseType: 'arraybuffer'
}, xhr.httpHandler(function(err, responseBody) {

  // we got an error if the XHR errored out or if the status code was 4xx/5xx
  if (err) {
    // error cause is coming soon to JavaScript https://github.com/tc39/proposal-error-cause
    throw new Error(err, {cause: err.cause});

  // this will log an ArrayBuffer

    uri: "https://example.com/foo",
    responseType: 'arraybuffer'
}, xhr.httpHandler(function(err, responseBody) {

  if (err) {
    throw new Error(err, {cause: err.cause});

  // in this case, responseBody will be a String

// passing true as the second argument will cause httpHandler try and decode the response body into a string


  • Why is my server's JSON response not parsed? I returned the right content-type.
- See options.json - you can set it to true on a GET request to tell xhr to parse the response body. - Without options.json body is returned as-is (a string or when responseType is set and the browser supports it - a result of parsing JSON or XML)
  • How do I send an object or array as POST body?
- options.body should be a string. You need to serialize your object before passing to xhr for sending. - To serialize to JSON you can use
`options.json:true` with `options.body` for convenience - then `xhr` will do the serialization and set content-type accordingly.
  • Where's stream API? .pipe() etc.
- Not implemented. You can't reasonably have that in the browser.
  • Why can't I send "true" as body by passing it as options.json anymore?
- Accepting true as a value was a bug. Despite what JSON.stringify does, the string "true" is not valid JSON. If you're sending booleans as JSON, please consider wrapping them in an object or array to save yourself from more trouble in the future. To bring back the old behavior, hardcode options.json to true and set options.body to your boolean value.
  • How do I add an onprogress listener?
- use beforeSend function for non-standard things that are browser specific. In this case: ```js xhr({
beforeSend: function(xhrObject){
  xhrObject.onprogress = function(){}
}) ```

Mocking Requests

You can override the constructor used to create new requests for testing. When you're making a new request:
xhr({ xhr: new MockXMLHttpRequest() })

or you can override the constructors used to create requests at the module level:
xhr.XMLHttpRequest = MockXMLHttpRequest
xhr.XDomainRequest = MockXDomainRequest

MIT Licenced

1: http://xhr.spec.whatwg.org/#the-send()-method 2: http://xhr.spec.whatwg.org/#the-open()-method 3: http://xhr.spec.whatwg.org/#interface-xmlhttprequest 4: http://msdn.microsoft.com/en-us/library/ie/cc288060(v=vs.85).aspx 5: http://es5.github.com/#x15.11 6: http://xhr.spec.whatwg.org/#the-response-attribute 7: http://xhr.spec.whatwg.org/#the-responsetext-attribute 8: http://xhr.spec.whatwg.org/#the-responsexml-attribute 9: http://xhr.spec.whatwg.org/#the-setrequestheader()-method 10: http://xhr.spec.whatwg.org/#the-withcredentials-attribute 11: https://xhr.spec.whatwg.org/#the-responsetype-attribute