"this" keyword in nodejs does'nt get update when you export new object

December 8, 2022

i have this code in nodejs (commonjs) v14.16.1


module.exports.varOne = 'one'

module.exports = {varTwo: 'two', ...module.exports}

console.log('module', module);
console.log(this, this === module.exports);

and this is the results after running it

module Module {
  id: '.',
  path: '...',
  exports: { varTwo: 'two', varOne: 'one' },
  parent: null,
  filename: '...',
  loaded: false,
  children: [],
  paths: [...]
}
{ varOne: 'one' } false

I don’t understand why "this" here doesn’t change to the new exports? please help.

>Solution :

In Javascript, the value of this doesn’t change within a given code context like this. That’s how the language itself works.

You replaced the given exports object with a different object. Nothing in the language will cause that assignment to change the value of this. The value of this still points at the original exports object.

Fortunately, this isn’t a problem in nodejs as you have multiple work-arounds. You can either not replace the exports object (just assign values to the existing one) or you can use module.exports to refer to the new object instead of this.

FYI, you will notice the same thing with the exports variable. It will still point at the original exports object too.