How to Use events. emitter. once in node. js _ node. js-js tutorial

This article mainly introduces node. events. emitter. once method usage instructions, this article introduces events. emitter. once method description, syntax, receive parameters, use instances, and implement Source Code. For more information, see Method description:

Registers a single listener for a specified event. Therefore, the listener is triggered only once at most, and the listener is immediately removed after the event is triggered.

Syntax:

The Code is as follows:

Emitter. once (event, listener)

Receiving parameters:

Event (string) event Type

The callback function when the listener (function) triggers an event.

Example:

The Code is as follows:

Server. once ('connection', function (stream ){
Console. log ('Ah, we have our first user! ');
});

Source code:

The Code is as follows:

EventEmitter. prototype. once = function (type, listener ){
If (! Util. isFunction (listener ))
Throw TypeError ('listener must be a function ');
Function g (){
This. removeListener (type, g );
Listener. apply (this, arguments );
}
G. listener = listener;
This. on (type, g );
Return this;
};