In node.js "request.on" what is it this ".on"

Question

In node.js "request.on" what is it this ".on"

I'm new in node.js and java script, i cant find meaning of this ".on" keyword. when i change it with another word code failed.

var req = http.get("http://www.google.com", function(res) {
  console.log("Got response: " + res.statusCode);

 res.**on**('data', function (chunk) {
});

}).**on**('error', function(e) {
console.log("Got error: " + e.message);
 });

javascript
node.js

Answer 1

The on method binds an event to a object.

It is a way to express your intent if there is something happening (data sent or error in your case) , then execute the function added as a parameter. This style of programming is called Event-driven programming. You might want to look it up in the Wikipedia

In node.js, there is a class called EventEmitter that provides you with all the code that you need for basic events if you decide to use them in your own code (which I would strongly recommend in the case of node.js). Docs for node.js EventEmitter are here

Answer 2

.on is a method use to bind event handler.