CODEWITHSUNDEEP
javascriptnode.jssetinterval
Jazcash
Jazcash

Reputation: 3314

Why does clearinterval change thing in this code?

var interval = setInterval(function (){
    console.log("Hello world");
}, 1000);

var thing = interval;
console.log(thing);
clearInterval(interval);
console.log("interval cleared");
console.log(thing);

thing is printed differently before and after clearing interval and I can't understand why. Halp pls?

Edit: Sorry, I should've been clearer. I'm using node.js, and this is the output to the above code:

{ _idleTimeout: 1000,
  _idlePrev: 
   { _idleNext: [Circular],
     _idlePrev: [Circular],
     msecs: 1000,
     ontimeout: [Function: listOnTimeout] },
  _idleNext: 
   { _idleNext: [Circular],
     _idlePrev: [Circular],
     msecs: 1000,
     ontimeout: [Function: listOnTimeout] },
  _idleStart: 1394616963526,
  _onTimeout: [Function: wrapper],
  _repeat: true }
interval cleared
{ _idleTimeout: -1,
  _idlePrev: null,
  _idleNext: null,
  _idleStart: 1394616963526,
  _onTimeout: null,
  _repeat: false,
  ontimeout: null }

Why is thing affected by the clearInterval at all?

Upvotes: 0

Views: 75

Answers (2)

xdazz
xdazz

Reputation: 160853

clearInterval(interval); is used to cancel the repeated action which was set up by setInterval.

But in your code, thing is assigned before clearInterval(interval);, so it will not printed differently.

Update:

Things are different in node.js, in nodejs, setInterval returns an Timer object but not a number. So clear interval will clear thing too, because they refer to same object.

Upvotes: 1

Barmar
Barmar

Reputation: 781068

The two variables interval and thing both refer to the same Timer object. When you call clearInterval, it modifies that object, and this is what console.log shows.

It's similar to the following code:

var obj1 = { a : 3 };
var obj2 = obj1;
obj1.a = 4;
console.log(obj2);

This will log { a : 4 }. If you want the two variables to refer to different objects, you need to clone the object; see

What is the most efficient way to deep clone an object in JavaScript?

Upvotes: 1

Related Questions