Node.js Cannot read property 'on' of undefined
25,212
Solution 1
You forgot to return the event emitter from your v
function:
var v = function() {
var e = new events();
e.emit('start');
return e;
};
Also notice that the start
event will not be called because you have emitted the event before you subscribed to it. So you could kind of rework your code a little:
var events = require('events').EventEmitter;
var v = function() {
var e = new events();
return e;
};
var r = v();
r.on('start', function(){
console.log('event start just fired!!!!!!!!!!');
});
// emit the event after you have subscribed to the start callback
r.emit('start');
Solution 2
r
is undefined, since v
isn't returning anything. That's why you're getting the error. And even if you return the event, your code won't give you the desired output, since you need to use on("start")
before you use emit("start")
var events = require('events').EventEmitter;
var e = new events();
e.emit('start'); //This won't trigger the console.log
//Need to be binded before you emit the event.
e.on('start', function(){
console.log('event start just fired!!!!!!!!!!');
});
e.emit('start'); //This will trigger the console.log
Author by
Milad
Updated on July 09, 2022Comments
-
Milad almost 2 years
What is wrong?
p.s. : I am new to node.js and I'm from .Net world!
My server.js code :
var events = require('events').EventEmitter; var v = function() { var e = new events(); e.emit('start'); }; var r = v(); r.on('start', function(){ console.log('event start just fired!!!!!!!!!!'); });
and this console output :
TypeError: Cannot read property 'on' of undefined at Object.<anonymous> (E:\Project\node\BasicSocial\server.js:12:2) at Module._compile (module.js:410:26) at Object.Module._extensions..js (module.js:417:10) at Module.load (module.js:344:32) at Function.Module._load (module.js:301:12) at Function.Module.runMain (module.js:442:10) at startup (node.js:136:18) at node.js:966:3