Javascript function closure - access updated variable value in return statement

Question

I'm working with a nested function similar to the one below:

function counter() {
  let count = 0;

  function increment() {
    count++;
  }

  return {
    count: () => count,
    increment: increment
  };
}

const myCounter = counter();
myCounter.increment();
console.log(myCounter.count())

This appears to work fine but is there any way to return the updated count as just the value instead of a function? Ideally the goal is to be able to access the updated count with just myCounter.count instead of myCounter.count()

Your function count: () => count is a function that returns by value. — THG
– THG, Commented Apr 9, 2020 at 15:15
@TLane Can you elaborate? I'm not sure what you're trying to say. — Dave Newton
– Dave Newton, Commented Apr 9, 2020 at 16:13
Your function returns by a copy of count. The lambda function you have returns by value, and it cannot do any sort of this-pointer binding. If you want an object with a function that returns an incremented copy, make it like so: counter = {count: 0, increment: function(){return ++this.count;}} — THG
– THG, Commented Apr 12, 2020 at 17:30

Nina Scholz · Accepted Answer · 2020-04-09 15:12:05Z

2

You could take a getter, which is a function which is called if you use the property.

function counter() {
  let count = 0;

  function increment() {
    count++;
  }

  return {
    get count() { return count },
    increment
  };
}

const myCounter = counter();
myCounter.increment();
console.log(myCounter.count)

answered Apr 9, 2020 at 15:12

Nina Scholz

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Comments

xdeepakv · Accepted Answer · 2020-04-09 15:13:52Z

0

You can use ES6 class, getter setter to simplify.

class Counter {
  constructor(){
    this._count = 0
  }
  increment() {
    this._count++;
  }
  get count(){
    return this._count;
  }
}


const myCounter = new Counter();
myCounter.increment();
myCounter.increment();
console.log(myCounter.count)

edited Apr 9, 2020 at 15:13

answered Apr 9, 2020 at 15:11

xdeepakv

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4 Comments

Dave Newton Over a year ago

True, but OP is (currently, at least) working specifically with the code provided. It may or may not be trivial to adjust the code they're using.

xdeepakv Over a year ago

@DaveNewton It s safe and secure and more readable. compare to function. and less error-prone like this. not found. I don't see any point not suggesting something better to learn. I have written also, using ES6. Else it can be done using defined property, which is more complex to understand

xdeepakv Over a year ago

Let's OP to deside whether he/she want to learn new thing, rather than stick to old thing.

Dave Newton Over a year ago

My point is simple: showing an alternative is fine, but does not directly answer the question (and the more-appropriate answer shows that it's not any more complex).

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