CODEWITHSUNDEEP
javascriptfunctionvariablesclosures
31113
31113

Reputation: 409

Increments changing every function run as variable

I have found the simple solution here using closure from @Xotic750

But, Is it possible to run function without round brackets? E.G.:

var increment = new Increment()

console.log('value: ' + increment) // value: 1
console.log('value: ' + increment) // value: 2
console.log('value: ' + increment) // value: 3

Every function run I have got the function as [object Object] in console.log instead of value :

    var Increment = (function(n) {
      return function() {
        n += 1;
        return n;
      }
    }(0)); 

    var increment = new Increment();

    console.log('value: ' + increment) // value: [object Object]
    console.log('value: ' + increment) // value: [object Object]
    console.log('value: ' + increment) // value: [object Object]

Upvotes: 0

Views: 75

Answers (3)

trincot
trincot

Reputation: 350477

As you are printing the increment instances, there is a toString conversion happening. You could use that to perform the increment:

var Increment = (function(n) {
  var f = function() {}; // Only serves as constructor
  f.prototype.toString = function() {
    n += 1;
    return n;
  }
  return f
}(0)); 

var increment = new Increment();

console.log('value: ' + increment) // value: 1
console.log('value: ' + increment) // value: 2
console.log('value: ' + increment) // value: 3

Be aware, the counter is kinda global. If you want the counter to be separate and restart from 0 for each instance, then use this:

var Increment = (function(n) {
  var f = function() {
      this.n = 0;
  };
  f.prototype.toString = function() {
    this.n += 1;
    return this.n;
  }
  return f
}(0)); 

var increment = new Increment();

console.log('value: ' + increment) // value: 1
console.log('value: ' + increment) // value: 2
console.log('value: ' + increment) // value: 3

increment = new Increment();

console.log('value: ' + increment) // value: 1
console.log('value: ' + increment) // value: 2
console.log('value: ' + increment) // value: 3

Upvotes: 2

Titus
Titus

Reputation: 22474

Is it possible to run function without round brackets

Yes, you can do that using a getter, here is an example:

class Cls {
   constructor() {
      this.value = 0;
   }
   get increment() {
      return this.value++
   }
}

const cls = new Cls()

console.log('value: ' + cls.increment)
console.log('value: ' + cls.increment)
console.log('value: ' + cls.increment)

Upvotes: 1

Ben
Ben

Reputation: 2706

You are creating an object of the function Increment by using the new keyword. In your case, you would simply want to call the Increment function as so:

console.log('value: ' + Increment());
console.log('value: ' + Increment());
console.log('value: ' + Increment());

See this link on Closures for a more detailed explanation as to how they work.

Upvotes: 1

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