CODEWITHSUNDEEP
javascript
Sasha Kos
Sasha Kos

Reputation: 2608

Function with previous state saving

I have a code

var variable = 0;

function add() {
  return variable += 1;
}

console.log(add());
console.log(add());

Im wonder is there a way to write this code only using function and scope, smth like

function add() {
  /* SET INITIAL STATE IF NOT SET*/
  /* EXECUTE */
  /* RETURN NEW VAL */
}

add(); /* RETURN 1*/
add(); /* RETURN 2*/

to get the same result.

Thank you.

Upvotes: 0

Views: 64

Answers (3)

joaner
joaner

Reputation: 716

Also could see the yield operator (generator functions), or console.count()

var add = function () {
  var generate = function *inc() {
    var i = 0
    do {
      i++
      yield i
    } while(true)
  }()
  return function() {
    return generate.next().value
  }
}()

console.log(add())
console.log(add())
console.log(add())

Upvotes: 0

T.J. Crowder
T.J. Crowder

Reputation: 1074276

...only using one function...

Your code does use only one function (add). If you mean you don't want it to close over variable, you can store the count elsewhere, for instance as a property on the function itself:

function add() {
  if (!add.variable) {
    add.variable = 0;
  }
  return ++add.variable;
}

console.log(add());
console.log(add());
console.log(add());

But of course, that means any code can access and change it.

The usual thing is to close over the variable, and perhaps hide it in a scope where nothing else can see it:

var add = (function() {
  var variable = 0;
  return function add() {
    return ++variable;
  };
})();

console.log(add());
console.log(add());
console.log(add());

Upvotes: 5

KooiInc
KooiInc

Reputation: 122906

You can create a pseudo static variable for the function:

(() => {
  document.querySelector("#test").addEventListener("click", () => console.log(add(1)));
  function add(n) {
    add.constant = add.constant || 0;
    add.constant += n;
    return add.constant;
  }
})()
<button id="test">add 1</button>

Upvotes: 1

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