Request

A Koa Request object is an abstraction on top of node's vanilla request object, providing additional functionality that is useful for every day HTTP server development.

API

request.headers

Request header object. Alias as request.header.

request.headers=

Set request header object. Alias as request.header=.

request.method=

Set request method, useful for implementing middleware such as methodOverride().

request.length

Return request Content-Length as a number when present, or undefined.

request.url=

Set request URL, useful for url rewrites.

request.origin

Get origin of URL, include protocol and host.

ctx.request.origin
// => http://example.com

request.href

Get full request URL, include protocol, host and url.

ctx.request.href;
// => http://example.com/foo/bar?q=1

request.path=

Set request pathname and retain query-string when present.

request.host

Get host (hostname:port) when present. Supports X-Forwarded-Host when app.proxy is true, otherwise Host is used.

request.hostname

Get hostname when present. Supports X-Forwarded-Host when app.proxy is true, otherwise Host is used.

If host is IPv6, Koa delegates parsing to WHATWG URL API, Note This may impact performance.

request.type

Get request Content-Type void of parameters such as "charset".

const ct = ctx.request.type;
// => "image/png"

request.charset

Get request charset when present, or undefined:

ctx.request.charset;
// => "utf-8"

request.query

Get parsed query-string, returning an empty object when no query-string is present. Note that this getter does not support nested parsing.

For example "color=blue&size=small":

{
  color: 'blue',
  size: 'small'
}

request.query=

Set query-string to the given object. Note that this setter does not support nested objects.

ctx.query = { next: '/login' };

Check if a request cache is "fresh", aka the contents have not changed. This method is for cache negotiation between If-None-Match / ETag, and If-Modified-Since and Last-Modified. It should be referenced after setting one or more of these response headers.

// freshness check requires status 20x or 304
ctx.status = 200;
ctx.set('ETag', '123');

// cache is ok
if (ctx.fresh) {
  ctx.status = 304;
  return;
}

// cache is stale
// fetch new data
ctx.body = await db.find('something');

request.stale

Inverse of request.fresh.

request.protocol

Return request protocol, "https" or "http". Supports X-Forwarded-Proto when app.proxy is true.

request.secure

Shorthand for ctx.protocol == "https" to check if a request was issued via TLS.

request.ip

Request remote address. Supports X-Forwarded-For when app.proxy is true.

request.ips

When X-Forwarded-For is present and app.proxy is enabled an array of these ips is returned, ordered from upstream -> downstream. When disabled an empty array is returned.

request.subdomains

Return subdomains as an array.

Subdomains are the dot-separated parts of the host before the main domain of the app. By default, the domain of the app is assumed to be the last two parts of the host. This can be changed by setting app.subdomainOffset.

For example, if the domain is "tobi.ferrets.example.com": If app.subdomainOffset is not set, ctx.subdomains is ["ferrets", "tobi"]. If app.subdomainOffset is 3, ctx.subdomains is ["tobi"].

request.is(types...)

Check if the incoming request contains the "Content-Type" header field, and it contains any of the give mime types. If there is no request body, null is returned. If there is no content type, or the match fails false is returned. Otherwise, it returns the matching content-type.

// With Content-Type: text/html; charset=utf-8
ctx.is('html'); // => 'html'
ctx.is('text/html'); // => 'text/html'
ctx.is('text/*', 'text/html'); // => 'text/html'

// When Content-Type is application/json
ctx.is('json', 'urlencoded'); // => 'json'
ctx.is('application/json'); // => 'application/json'
ctx.is('html', 'application/*'); // => 'application/json'

ctx.is('html'); // => false

For example if you want to ensure that only images are sent to a given route:

if (ctx.is('image/*')) {
  // process
} else {
  ctx.throw(415, 'images only!');
}

Content Negotiation

Koa's request object includes helpful content negotiation utilities powered by accepts and negotiator. These utilities are:

request.accepts(types)
request.acceptsEncodings(types)
request.acceptsCharsets(charsets)
request.acceptsLanguages(langs)

If no types are supplied, all acceptable types are returned.

If multiple types are supplied, the best match will be returned. If no matches are found, a false is returned, and you should send a 406 "Not Acceptable" response to the client.

In the case of missing accept headers where any type is acceptable, the first type will be returned. Thus, the order of types you supply is important.

request.accepts(types)

Check if the given type(s) is acceptable, returning the best match when true, otherwise false. The type value may be one or more mime type string such as "application/json", the extension name such as "json", or an array ["json", "html", "text/plain"].

// Accept: text/html
ctx.accepts('html');
// => "html"

// Accept: text/*, application/json
ctx.accepts('html');
// => "html"
ctx.accepts('text/html');
// => "text/html"
ctx.accepts('json', 'text');
// => "json"
ctx.accepts('application/json');
// => "application/json"

// Accept: text/*, application/json
ctx.accepts('image/png');
ctx.accepts('png');
// => false

// Accept: text/*;q=.5, application/json
ctx.accepts(['html', 'json']);
ctx.accepts('html', 'json');
// => "json"

// No Accept header
ctx.accepts('html', 'json');
// => "html"
ctx.accepts('json', 'html');
// => "json"

You may call ctx.accepts() as many times as you like, or use a switch:

switch (ctx.accepts('json', 'html', 'text')) {
  case 'json': break;
  case 'html': break;
  case 'text': break;
  default: ctx.throw(406, 'json, html, or text only');
}

request.acceptsEncodings(encodings)

Check if encodings are acceptable, returning the best match when true, otherwise false. Note that you should include identity as one of the encodings!

// Accept-Encoding: gzip
ctx.acceptsEncodings('gzip', 'deflate', 'identity');
// => "gzip"

ctx.acceptsEncodings(['gzip', 'deflate', 'identity']);
// => "gzip"

When no arguments are given all accepted encodings are returned as an array:

// Accept-Encoding: gzip, deflate
ctx.acceptsEncodings();
// => ["gzip", "deflate", "identity"]

Note that the identity encoding (which means no encoding) could be unacceptable if the client explicitly sends identity;q=0. Although this is an edge case, you should still handle the case where this method returns false.

request.acceptsCharsets(charsets)

Check if charsets are acceptable, returning the best match when true, otherwise false.

// Accept-Charset: utf-8, iso-8859-1;q=0.2, utf-7;q=0.5
ctx.acceptsCharsets('utf-8', 'utf-7');
// => "utf-8"

ctx.acceptsCharsets(['utf-7', 'utf-8']);
// => "utf-8"

When no arguments are given all accepted charsets are returned as an array:

// Accept-Charset: utf-8, iso-8859-1;q=0.2, utf-7;q=0.5
ctx.acceptsCharsets();
// => ["utf-8", "utf-7", "iso-8859-1"]

request.acceptsLanguages(langs)

Check if langs are acceptable, returning the best match when true, otherwise false.

// Accept-Language: en;q=0.8, es, pt
ctx.acceptsLanguages('es', 'en');
// => "es"

ctx.acceptsLanguages(['en', 'es']);
// => "es"

When no arguments are given all accepted languages are returned as an array:

// Accept-Language: en;q=0.8, es, pt
ctx.acceptsLanguages();
// => ["es", "pt", "en"]