javascript - ES6 Class and module.exports - Stack Overflow

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I am seeing this pattern these days for nodeJS implementation, where in we have the following code for my Module:

class Foo {
  bar() {
    console.log('bar');
  }
}
module.exports = Foo;

Then when I do a require and finally say new to create an instance of the class.

var Foo = require(./foo);
var myFoo = new Foo();
myFoo.bar();

This pattern according to me will keep creating multiple instances of class Foo, everytime it is called.

The other pattern could have been what i am used to where in my foo.js would be.

module.exports = {
  bar: function() {
    console.log('bar');
  }
};

And then i just require and call bar.

var foo = require(./foo);
foo.bar();

Question would these two behave the same? Will the second pattern keep creating objects everytime I require and call bar on the object?

Isn't creating singleton pattern a good idea in case 1 as we are used to in other languages, wherein we keep serving the same instance if it has already been created once?

I am seeing this pattern these days for nodeJS implementation, where in we have the following code for my Module:

class Foo {
  bar() {
    console.log('bar');
  }
}
module.exports = Foo;

Then when I do a require and finally say new to create an instance of the class.

var Foo = require(./foo);
var myFoo = new Foo();
myFoo.bar();

This pattern according to me will keep creating multiple instances of class Foo, everytime it is called.

The other pattern could have been what i am used to where in my foo.js would be.

module.exports = {
  bar: function() {
    console.log('bar');
  }
};

And then i just require and call bar.

var foo = require(./foo);
foo.bar();

Question would these two behave the same? Will the second pattern keep creating objects everytime I require and call bar on the object?

Isn't creating singleton pattern a good idea in case 1 as we are used to in other languages, wherein we keep serving the same instance if it has already been created once?

• javascript
• node.js
• ecmascript-6

Share Improve this question Follow edited Sep 16, 2016 at 9:31 Bergi 665k161161 gold badges1k1k silver badges1.5k1.5k bronze badges asked Sep 16, 2016 at 8:56 Sourav ChatterjeeSourav Chatterjee 81022 gold badges1414 silver badges2929 bronze badges 2

• you are using ES6 so be sure that, very few browser support this feature. – arjun kori Commented Sep 16, 2016 at 9:01
• The intention is to run in nodeJS and not in browser. – Sourav Chatterjee Commented Sep 16, 2016 at 9:29

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1 Answer 1

Sorted by: Reset to default 10

This pattern according to me will keep creating multiple instances of class Foo, everytime it is called.

Yes, that's the purpose. Though new Foo(); is only executed once in your example as well.

would these two behave the same?

No.

Will the second pattern keep creating objects everytime I require and call bar on the object?

No. require() calls are cached, they return the same module every time.

Isn't creating singleton pattern a good idea?

No, a singleton is rarely a good idea if it contains any state. Your example does not, but where classes are used in Node.js they usually do.

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