25 KiB
SuperAgent
SuperAgent is light-weight progressive ajax API crafted for flexibility, readability, and a low learning curve after being frustrated with many of the existing request APIs. It also works with Node.js!
request
.post('/api/pet')
.send({ name: 'Manny', species: 'cat' })
.set('X-API-Key', 'foobar')
.set('Accept', 'application/json')
.end(function(err, res){
if (err || !res.ok) {
alert('Oh no! error');
} else {
alert('yay got ' + JSON.stringify(res.body));
}
});
Test documentation
The following test documentation was generated with Mocha's "doc" reporter, and directly reflects the test suite. This provides an additional source of documentation.
Request basics
A request can be initiated by invoking the appropriate method on the request object, then calling .end() to send the request. For example a simple GET request:
request
.get('/search')
.end(function(err, res){
});
A method string may also be passed:
request('GET', '/search').end(callback);
ES6 promises are supported. Instead of .end() you can call .then():
request('GET', '/search').then(success, failure);
The Node client may also provide absolute URLs. In browsers absolute URLs won't work unless the server implements CORS.
request
.get('http://example.com/search')
.end(function(err, res){
});
The Node client supports making requests to Unix Domain Sockets:
// pattern: https?+unix://SOCKET_PATH/REQUEST_PATH
// Use `%2F` as `/` in SOCKET_PATH
request
.get('http+unix://%2Fabsolute%2Fpath%2Fto%2Funix.sock/search')
.end(function(err, res){
});
DELETE, HEAD, PATCH, POST, and PUT requests can also be used, simply change the method name:
request
.head('/favicon.ico')
.end(function(err, res){
});
DELETE can be also called as .del() for compatibility with old IE where delete is a reserved word.
The HTTP method defaults to GET, so if you wish, the following is valid:
request('/search', function(err, res){
});
Setting header fields
Setting header fields is simple, invoke .set() with a field name and value:
request
.get('/search')
.set('API-Key', 'foobar')
.set('Accept', 'application/json')
.end(callback);
You may also pass an object to set several fields in a single call:
request
.get('/search')
.set({ 'API-Key': 'foobar', Accept: 'application/json' })
.end(callback);
GET requests
The .query() method accepts objects, which when used with the GET method will form a query-string. The following will produce the path /search?query=Manny&range=1..5&order=desc.
request
.get('/search')
.query({ query: 'Manny' })
.query({ range: '1..5' })
.query({ order: 'desc' })
.end(function(err, res){
});
Or as a single object:
request
.get('/search')
.query({ query: 'Manny', range: '1..5', order: 'desc' })
.end(function(err, res){
});
The .query() method accepts strings as well:
request
.get('/querystring')
.query('search=Manny&range=1..5')
.end(function(err, res){
});
Or joined:
request
.get('/querystring')
.query('search=Manny')
.query('range=1..5')
.end(function(err, res){
});
HEAD requests
You can also use the .query() method for HEAD requests. The following will produce the path /users?email=joe@smith.com.
request
.head('/users')
.query({ email: 'joe@smith.com' })
.end(function(err, res){
});
POST / PUT requests
A typical JSON POST request might look a little like the following, where we set the Content-Type header field appropriately, and "write" some data, in this case just a JSON string.
request.post('/user')
.set('Content-Type', 'application/json')
.send('{"name":"tj","pet":"tobi"}')
.end(callback)
Since JSON is undoubtedly the most common, it's the default! The following example is equivalent to the previous.
request.post('/user')
.send({ name: 'tj', pet: 'tobi' })
.end(callback)
Or using multiple .send() calls:
request.post('/user')
.send({ name: 'tj' })
.send({ pet: 'tobi' })
.end(callback)
By default sending strings will set the Content-Type to application/x-www-form-urlencoded,
multiple calls will be concatenated with &, here resulting in name=tj&pet=tobi:
request.post('/user')
.send('name=tj')
.send('pet=tobi')
.end(callback);
SuperAgent formats are extensible, however by default "json" and "form" are supported. To send the data as application/x-www-form-urlencoded simply invoke .type() with "form", where the default is "json". This request will POST the body "name=tj&pet=tobi".
request.post('/user')
.type('form')
.send({ name: 'tj' })
.send({ pet: 'tobi' })
.end(callback)
Sending a FormData object is also supported. The following example will POST the content of the HTML form identified by id="myForm":
request.post('/user')
.send(new FormData(document.getElementById('myForm')))
.end(callback)
Setting the Content-Type
The obvious solution is to use the .set() method:
request.post('/user')
.set('Content-Type', 'application/json')
As a short-hand the .type() method is also available, accepting
the canonicalized MIME type name complete with type/subtype, or
simply the extension name such as "xml", "json", "png", etc:
request.post('/user')
.type('application/json')
request.post('/user')
.type('json')
request.post('/user')
.type('png')
Serializing request body
SuperAgent will automatically serialize JSON and forms. If you want to send the payload in a custom format, you can replace the built-in serialization with .serialize() method.
Retrying requests
When given the .retry() method, SuperAgent will automatically retry requests, if they fail in a way that is transient or could be due to a flaky Internet connection.
This method has two optional arguments: number of retries (default 3) and a callback. It calls callback(err, res) before each retry. The callback may return true/false to control whether the request sould be retried (but the maximum number of retries is always applied).
request
.get('http://example.com/search')
.retry(2)
.end(callback);
Use .retry() only with requests that are idempotent (i.e. multiple requests reaching the server won't cause undesirable side effects like duplicate purchases).
Setting Accept
In a similar fashion to the .type() method it is also possible to set the Accept header via the short hand method .accept(). Which references request.types as well allowing you to specify either the full canonicalized MIME type name as type/subtype, or the extension suffix form as "xml", "json", "png", etc. for convenience:
request.get('/user')
.accept('application/json')
request.get('/user')
.accept('json')
request.post('/user')
.accept('png')
Facebook and Accept JSON
If you are calling Facebook's API, be sure to send an Accept: application/json header in your request. If you don't do this, Facebook will respond with Content-Type: text/javascript; charset=UTF-8, which SuperAgent will not parse and thus res.body will be undefined. You can do this with either req.accept('json') or req.header('Accept', 'application/json'). See issue 1078 for details.
Query strings
req.query(obj) is a method which may be used to build up a query-string. For example populating ?format=json&dest=/login on a POST:
request
.post('/')
.query({ format: 'json' })
.query({ dest: '/login' })
.send({ post: 'data', here: 'wahoo' })
.end(callback);
By default the query string is not assembled in any particular order. An asciibetically-sorted query string can be enabled with req.sortQuery(). You may also provide a custom sorting comparison function with req.sortQuery(myComparisonFn). The comparison function should take 2 arguments and return a negative/zero/positive integer.
// default order
request.get('/user')
.query('name=Nick')
.query('search=Manny')
.sortQuery()
.end(callback)
// customized sort function
request.get('/user')
.query('name=Nick')
.query('search=Manny')
.sortQuery(function(a, b){
return a.length - b.length;
})
.end(callback)
TLS options
In Node.js SuperAgent supports methods to configure HTTPS requests:
.ca(): Set the CA certificate(s) to trust.cert(): Set the client certificate chain(s).key(): Set the client private key(s).pfx(): Set the client PFX or PKCS12 encoded private key and certificate chain
For more information, see Node.js https.request docs.
var key = fs.readFileSync('key.pem'),
cert = fs.readFileSync('cert.pem');
request
.post('/client-auth')
.key(key)
.cert(cert)
.end(callback);
var ca = fs.readFileSync('ca.cert.pem');
request
.post('https://localhost/private-ca-server')
.ca(ca)
.end(callback);
Parsing response bodies
SuperAgent will parse known response-body data for you, currently supporting application/x-www-form-urlencoded, application/json, and multipart/form-data.
You can set a custom parser (that takes precedence over built-in parsers) with the .buffer(true).parse(fn) method. If response buffering is not enabled (.buffer(false)) then the response event will be emitted without waiting for the body parser to finish, so response.body won't be available.
JSON / Urlencoded
The property res.body is the parsed object, for example if a request responded with the JSON string '{"user":{"name":"tobi"}}', res.body.user.name would be "tobi". Likewise the x-www-form-urlencoded value of "user[name]=tobi" would yield the same result. Only one level of nesting is supported. If you need more complex data, send JSON instead.
Arrays are sent by repeating the key. .send({color: ['red','blue']}) sends color=red&color=blue. If you want the array keys to contain [] in their name, you must add it yourself, as SuperAgent doesn't add it automatically.
Multipart
The Node client supports multipart/form-data via the Formidable module. When parsing multipart responses, the object res.files is also available to you. Suppose for example a request responds with the following multipart body:
--whoop
Content-Disposition: attachment; name="image"; filename="tobi.png"
Content-Type: image/png
... data here ...
--whoop
Content-Disposition: form-data; name="name"
Content-Type: text/plain
Tobi
--whoop--
You would have the values res.body.name provided as "Tobi", and res.files.image as a File object containing the path on disk, filename, and other properties.
Binary
In browsers, you may use .responseType('blob') to request handling of binary response bodies. This API is unnecessary when running in node.js. The supported argument values for this method are
'blob'passed through to the XmlHTTPRequestresponseTypeproperty'arraybuffer'passed through to the XmlHTTPRequestresponseTypeproperty
req.get('/binary.data')
.responseType('blob')
.end(function (error, res) {
// res.body will be a browser native Blob type here
});
For more information, see the Mozilla Developer Network xhr.responseType docs.
Response properties
Many helpful flags and properties are set on the Response object, ranging from the response text, parsed response body, header fields, status flags and more.
Response text
The res.text property contains the unparsed response body string. This property is always present for the client API, and only when the mime type matches "text/", "/json", or "x-www-form-urlencoded" by default for node. The reasoning is to conserve memory, as buffering text of large bodies such as multipart files or images is extremely inefficient. To force buffering see the "Buffering responses" section.
Response body
Much like SuperAgent can auto-serialize request data, it can also automatically parse it. When a parser is defined for the Content-Type, it is parsed, which by default includes "application/json" and "application/x-www-form-urlencoded". The parsed object is then available via res.body.
Response header fields
The res.header contains an object of parsed header fields, lowercasing field names much like node does. For example res.header['content-length'].
Response Content-Type
The Content-Type response header is special-cased, providing res.type, which is void of the charset (if any). For example the Content-Type of "text/html; charset=utf8" will provide "text/html" as res.type, and the res.charset property would then contain "utf8".
Response status
The response status flags help determine if the request was a success, among other useful information, making SuperAgent ideal for interacting with RESTful web services. These flags are currently defined as:
var type = status / 100 | 0;
// status / class
res.status = status;
res.statusType = type;
// basics
res.info = 1 == type;
res.ok = 2 == type;
res.clientError = 4 == type;
res.serverError = 5 == type;
res.error = 4 == type || 5 == type;
// sugar
res.accepted = 202 == status;
res.noContent = 204 == status || 1223 == status;
res.badRequest = 400 == status;
res.unauthorized = 401 == status;
res.notAcceptable = 406 == status;
res.notFound = 404 == status;
res.forbidden = 403 == status;
Aborting requests
To abort requests simply invoke the req.abort() method.
Timeouts
Sometimes networks and servers get "stuck" and never respond after accepting a request. Set timeouts to avoid requests waiting forever.
-
req.timeout({deadline:ms})orreq.timeout(ms)(wheremsis a number of milliseconds > 0) sets a deadline for the entire request (including all redirects) to complete. If the response isn't fully downloaded within that time, the request will be aborted. -
req.timeout({response:ms})sets maximum time to wait for the first byte to arrive from the server, but it does not limit how long the entire download can take. Response timeout should be a few seconds longer than just the time it takes server to respond, because it also includes time to make DNS lookup, TCP/IP and TLS connections.
You should use both deadline and response timeouts. This way you can use a short response timeout to detect unresponsive networks quickly, and a long deadline to give time for downloads on slow, but reliable, networks.
request
.get('/big-file?network=slow')
.timeout({
response: 5000, // Wait 5 seconds for the server to start sending,
deadline: 60000, // but allow 1 minute for the file to finish loading.
})
.end(function(err, res){
if (err.timeout) { /* timed out! */ }
});
Timeout errors have a .timeout property.
Authentication
In both Node and browsers auth available via the .auth() method:
request
.get('http://local')
.auth('tobi', 'learnboost')
.end(callback);
In the Node client Basic auth can be in the URL as "user:pass":
request.get('http://tobi:learnboost@local').end(callback);
By default only Basic auth is used. In browser you can add {type:'auto'} to enable all methods built-in in the browser (Digest, NTLM, etc.):
request.auth('digest', 'secret', {type:'auto'})
Following redirects
By default up to 5 redirects will be followed, however you may specify this with the res.redirects(n) method:
request
.get('/some.png')
.redirects(2)
.end(callback);
Agents for global state
Saving cookies
In Node SuperAgent does not save cookies by default, but you can use the .agent() method to create a copy of SuperAgent that saves cookies. Each copy has a separate cookie jar.
const agent = request.agent();
agent
.post('/login')
.then(() => {
return agent.get('/cookied-page');
});
In browsers cookies are managed automatically by the browser, so the .agent() does not isolate cookies.
Default options for multiple requests
Regular request methods (.use(), .set(), .auth()) called on the agent will be used as defaults for all requests made by that agent.
const agent = request.agent()
.use(plugin)
.auth(shared);
await agent.get('/with-plugin-and-auth');
await agent.get('/also-with-plugin-and-auth');
Piping data
The Node client allows you to pipe data to and from the request. For example piping a file's contents as the request:
const request = require('superagent');
const fs = require('fs');
const stream = fs.createReadStream('path/to/my.json');
const req = request.post('/somewhere');
req.type('json');
stream.pipe(req);
Note that when you pipe to a request, superagent sends the piped data with chunked transfer encoding, which isn't supported by all servers (for instance, Python WSGI servers).
Or piping the response to a file:
const stream = fs.createWriteStream('path/to/my.json');
const req = request.get('/some.json');
req.pipe(stream);
Note that you should NOT attempt to pipe the result of .end() or the Response object:
// Don't do either of these:
const stream = getAWritableStream();
const req = request
.get('/some.json')
// this pipes garbage to the stream and fails in unexpected ways
.end((err, response) => response.pipe(stream))
const req = request
.get('/some.json')
.end()
// this is also unsupported, .pipe calls .end for you.
.pipe(stream);
In a future version of superagent, improper calls to pipe() will fail.
Multipart requests
SuperAgent is also great for building multipart requests for which it provides methods .attach() and .field().
When you use .field() or .attach() you can't use .send() and you must not set Content-Type (the correct type will be set for you).
Attaching files
To send a file use .attach(name, [file], [options]). You can attach multiple files by calling .attach multiple times. The arguments are:
name— filed name in the form.file— either string with file path orBlob/Bufferobject.options— (optional) either string with custom file name or{filename: string}object. In Node also{contentType: 'mime/type'}is supported. In browser create aBlobwith an appropriate type instead.
request
.post('/upload')
.attach('image1', 'path/to/felix.jpeg')
.attach('image2', imageBuffer, 'luna.jpeg')
.field('caption', 'My cats')
.end(callback);
Field values
Much like form fields in HTML, you can set field values with .field(name, value) and .field({name: value}). Suppose you want to upload a few images with your name and email, your request might look something like this:
request
.post('/upload')
.field('user[name]', 'Tobi')
.field('user[email]', 'tobi@learnboost.com')
.field('friends[]', ['loki', 'jane'])
.attach('image', 'path/to/tobi.png')
.end(callback);
Compression
The node client supports compressed responses, best of all, you don't have to do anything! It just works.
Buffering responses
To force buffering of response bodies as res.text you may invoke req.buffer(). To undo the default of buffering for text responses such as "text/plain", "text/html" etc you may invoke req.buffer(false).
When buffered the res.buffered flag is provided, you may use this to handle both buffered and unbuffered responses in the same callback.
CORS
For security reasons, browsers will block cross-origin requests unless the server opts-in using CORS headers. Browsers will also make extra OPTIONS requests to check what HTTP headers and methods are allowed by the server. Read more about CORS.
The .withCredentials() method enables the ability to send cookies from the origin, however only when Access-Control-Allow-Origin is not a wildcard ("*"), and Access-Control-Allow-Credentials is "true".
request
.get('http://api.example.com:4001/')
.withCredentials()
.then(function(res){
assert.equal(200, res.status);
assert.equal('tobi', res.text);
})
Error handling
Your callback function will always be passed two arguments: error and response. If no error occurred, the first argument will be null:
request
.post('/upload')
.attach('image', 'path/to/tobi.png')
.end(function(err, res){
});
An "error" event is also emitted, with you can listen for:
request
.post('/upload')
.attach('image', 'path/to/tobi.png')
.on('error', handle)
.end(function(err, res){
});
Note that superagent considers 4xx and 5xx responses (as well as unhandled 3xx responses) errors by default. For example, if you get a 304 Not modified, 403 Forbidden or 500 Internal server error response, this status information will be available via err.status. Errors from such responses also contain an err.response field with all of the properties mentioned in "Response properties". The library behaves in this way to handle the common case of wanting success responses and treating HTTP error status codes as errors while still allowing for custom logic around specific error conditions.
Network failures, timeouts, and other errors that produce no response will contain no err.status or err.response fields.
If you wish to handle 404 or other HTTP error responses, you can query the err.status property. When an HTTP error occurs (4xx or 5xx response) the res.error property is an Error object, this allows you to perform checks such as:
if (err && err.status === 404) {
alert('oh no ' + res.body.message);
}
else if (err) {
// all other error types we handle generically
}
Alternatively, you can use the .ok(callback) method to decide whether a response is an error or not. The callback to the ok function gets a response and returns true if the response should be interpreted as success.
request.get('/404')
.ok(res => res.status < 500)
.then(response => {
// reads 404 page as a successful response
})
Progress tracking
SuperAgent fires progress events on upload and download of large files.
request.post(url)
.attach('field_name', file)
.on('progress', event => {
/* the event is:
{
direction: "upload" or "download"
percent: 0 to 100 // may be missing if file size is unknown
total: // total file size, may be missing
loaded: // bytes downloaded or uploaded so far
} */
})
.end()
Promise and Generator support
SuperAgent's request is a "thenable" object that's compatible with JavaScript promises and async/await syntax. Do not call .end() if you're using promises.
Libraries like co or a web framework like koa can yield on any SuperAgent method:
const req = request
.get('http://local')
.auth('tobi', 'learnboost');
const res = yield req;
Note that SuperAgent expects the global Promise object to be present. You'll need a polyfill to use promises in Internet Explorer or Node.js 0.10.
Browser and node versions
SuperAgent has two implementations: one for web browsers (using XHR) and one for Node.JS (using core http module). By default Browserify and WebPack will pick the browser version.
If want to use WebPack to compile code for Node.JS, you must specify node target in its configuration.
Using browser version in electron
Electron developers report if you would prefer to use the browser version of SuperAgent instead of the Node version, you can require('superagent/superagent'). Your requests will now show up in the Chrome developer tools Network tab. Note this environment is not covered by automated test suite and not officially supported.