Application this context belongs to.
Backend information for server that received the request.
// Backend name (usually "server", "cgi", or "mock")
const {name} = ctx.backend;
// Use low level Node.js APIs with "server" backend
const {res} = ctx.backend;
res.writeHead(200);
res.end('Hello World!');
Partial content. Always returns at least an empty string, even for sections that have not been defined with
ctx.contentFor()
.
// Get content for "head" section
const head = ctx.content.head;
Format for HTTP exceptions ("html", "json", or "txt").
WebSocket JSON mode.
Logger with request id.
// Pass logger with context to model
const log = ctx.log;
ctx.model.users.create({name: 'kraih'}, log);
Router dispatch plan.
HTTP request information.
// Extract request information
const id = ctx.req.requestId;
const method = ctx.req.method;
const baseURL = ctx.req.baseURL;
const url = ctx.req.url;
const query = ctx.req.query;
const info = ctx.req.userinfo;
const agent = ctx.req.get('User-Agent');
const buffer = await ctx.req.buffer();
const text = await ctx.req.text();
const form = await ctx.req.form();
const value = await ctx.req.json();
const html = await ctx.req.html();
const xml = await ctx.req.xml();
HTTP response information.
// Force file download by setting a response header
ctx.res.set('Content-Disposition', 'attachment; filename=foo.png;');
// Make sure response is cached correctly
ctx.res.set('Cache-Control', 'public, max-age=300');
ctx.res.headers.append('Vary', 'Accept-Encoding');
Non-persistent data storage and exchange for the current request.
Application config shortcut.
// Longer version
const config = ctx.app.config;
Home directory shortcut.
// Generate path
const path = ctx.home.child('views', 'foo', 'bar.html.tmpl');
Check if WebSocket connection has been accepted.
Check if WebSocket connection has been established.
Check if session is active.
Check if HTTP request is a WebSocket handshake.
Model shortcut.
// Access arbitrary model objects
const db = await ctx.models.pg.db();
Alias for emitter.on(eventName, listener)
.
Rest
...args: any[]v0.1.26
Append partial content to ctx.content
buffers.
// Add content for "head" section
await ctx.contentFor('head', '<link rel="icon" href="/static/favicon.ico">');
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();
// First listener
myEmitter.on('event', function firstListener() {
console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
const parameters = args.join(', ');
console.log(`event with parameters ${parameters} in third listener`);
});
console.log(myEmitter.listeners('event'));
myEmitter.emit('event', 1, 2, 3, 4, 5);
// Prints:
// [
// [Function: firstListener],
// [Function: secondListener],
// [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener
Rest
...args: any[]v0.1.26
Returns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbol
s.
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});
const sym = Symbol('symbol');
myEE.on(sym, () => {});
console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]
v6.0.0
Handle WebSocket upgrade, used by servers.
Accept WebSocket connection and activate JSON mode.
// Echo WebSocket messages
ctx.json(async ws => {
for await (const data of ws) {
// Add a Futurama quote to JSON objects
if (typeof data === 'object') {
data.quote = 'Shut up and take my money!';
await ws.send(data);
}
}
});
Returns the number of listeners listening for the event named eventName
.
If listener
is provided, it will return how many times the listener is found
in the list of the listeners of the event.
The name of the event being listened for
Optional
listener: FunctionThe event handler function
v3.2.0
Returns a copy of the array of listeners for the event named eventName
.
server.on('connection', (stream) => {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]
v0.1.26
Alias for emitter.removeListener()
.
Rest
...args: any[]v10.0.0
Adds the listener
function to the end of the listeners array for the
event named eventName
. No checks are made to see if the listener
has
already been added. Multiple calls passing the same combination of eventName
and listener
will result in the listener
being added, and called, multiple
times.
server.on('connection', (stream) => {
console.log('someone connected!');
});
Returns a reference to the EventEmitter
, so that calls can be chained.
By default, event listeners are invoked in the order they are added. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
The name of the event.
The callback function
Rest
...args: any[]v0.1.101
Adds a one-timelistener
function for the event named eventName
. The
next time eventName
is triggered, this listener is removed and then invoked.
server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});
Returns a reference to the EventEmitter
, so that calls can be chained.
By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
The name of the event.
The callback function
Rest
...args: any[]v0.3.0
GET and POST parameters.
// Get a specific parameter
const params = await ctx.params();
const foo = params.get('foo');
// Ignore all empty parameters
const params = await ctx.params({notEmpty: true});
Accept WebSocket connection.
// Echo incoming WebSocket messages
ctx.plain(async ws => {
for await (const message of ws) {
await ws.send(`echo: ${message}`);
}
});
Adds the listener
function to the beginning of the listeners array for the
event named eventName
. No checks are made to see if the listener
has
already been added. Multiple calls passing the same combination of eventName
and listener
will result in the listener
being added, and called, multiple
times.
server.prependListener('connection', (stream) => {
console.log('someone connected!');
});
Returns a reference to the EventEmitter
, so that calls can be chained.
The name of the event.
The callback function
Rest
...args: any[]v6.0.0
Adds a one-timelistener
function for the event named eventName
to the beginning of the listeners array. The next time eventName
is triggered, this
listener is removed, and then invoked.
server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});
Returns a reference to the EventEmitter
, so that calls can be chained.
The name of the event.
The callback function
Rest
...args: any[]v6.0.0
Returns a copy of the array of listeners for the event named eventName
,
including any wrappers (such as those created by .once()
).
import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));
// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];
// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();
// Logs "log once" to the console and removes the listener
logFnWrapper();
emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');
// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');
v9.4.0
Send 302
redirect response.
// Moved Permanently
await ctx.redirect_to('some_route', {status: 301});
Removes all listeners, or those of the specified eventName
.
It is bad practice to remove listeners added elsewhere in the code,
particularly when the EventEmitter
instance was created by some other
component or module (e.g. sockets or file streams).
Returns a reference to the EventEmitter
, so that calls can be chained.
Optional
event: string | symbolv0.1.26
Removes the specified listener
from the listener array for the event namedeventName
.
const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);
removeListener()
will remove, at most, one instance of a listener from the
listener array. If any single listener has been added multiple times to the
listener array for the specified eventName
, then removeListener()
must be
called multiple times to remove each instance.
Once an event is emitted, all listeners attached to it at the
time of emitting are called in order. This implies that anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
import { EventEmitter } from 'node:events';
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter();
const callbackA = () => {
console.log('A');
myEmitter.removeListener('event', callbackB);
};
const callbackB = () => {
console.log('B');
};
myEmitter.on('event', callbackA);
myEmitter.on('event', callbackB);
// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
// A
// B
// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
// A
Because listeners are managed using an internal array, calling this will
change the position indices of any listener registered after the listener
being removed. This will not impact the order in which listeners are called,
but it means that any copies of the listener array as returned by
the emitter.listeners()
method will need to be recreated.
When a single function has been added as a handler multiple times for a single
event (as in the example below), removeListener()
will remove the most
recently added instance. In the example the once('ping')
listener is removed:
import { EventEmitter } from 'node:events';
const ee = new EventEmitter();
function pong() {
console.log('pong');
}
ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);
ee.emit('ping');
ee.emit('ping');
Returns a reference to the EventEmitter
, so that calls can be chained.
Rest
...args: any[]v0.1.26
Render dynamic content.
Optional
stash: Record<string, any>// Render text
await ctx.render({text: 'Hello World!'});
// Render JSON
await ctx.render({json: {hello: 'world'}});
// Render view "users/list.*.*" and pass it a stash value
await ctx.render({view: 'users/list'}, {foo: 'bar'});
Try to render dynamic content to string.
Optional
stash: Record<string, any>Automatically select best possible representation for resource.
Get JSON schema validation function.
Persistent data storage for the next few requests.
By default EventEmitter
s will print a warning if more than 10
listeners are
added for a particular event. This is a useful default that helps finding
memory leaks. The emitter.setMaxListeners()
method allows the limit to be
modified for this specific EventEmitter
instance. The value can be set toInfinity
(or 0
) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter
, so that calls can be chained.
v0.3.5
Generate URL for route or path.
Optional
target: string// Current URL with query parameter
const url = ctx.urlFor('current', {query: {foo: 'bar'}});
// URL for route with placeholder values
const url = ctx.urlFor('users', {values: {id: 23}});
// Absolute URL for path with fragment
const url = ctx.urlFor('/some/path', {absolute: true, fragment: 'whatever'});
Generate URL for static asset.
Generate URL for static file.
Generate URL for route or path and preserve the current query parameters.
Optional
target: string// Remove a specific query parameter
const url = ctx.urlWith('current', {query: {foo: null}});
Generated using TypeDoc
Context class.