boolean does not change in function JavaScript

Question

I have the following code:

const ships = (length) => {
  isSunk = false
  console.log('BEFORE: ' + isSunk)
  const shipSize = length
  let hits = []
  const hitLocation = location => {
    hits.push(location);
    isSunk = true;
    console.log('INSIDE: ' + isSunk)
  }
  console.log('AFTER: ' + isSunk)
  return {
    isSunk,
    hitLocation,
    hits,
    shipSize
  }
}

const two = ships(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk)
console.log('HITS: ' + two.hits)

Is there a reason why isSunk is not saved as true when I call it in the end?

Is it due to the nested functions?

Answer 1

When you set the boolean into the object, it is that value. It is not a reference to the variable. So when you change the variable, the value you saved inside of the object that you returned is not updated.

You can use a function to get the value

const ships = (length) => {
  isSunk = false
  console.log('BEFORE: ' + isSunk)
  const shipSize = length
  let hits = []
  const hitLocation = location => {
    hits.push(location);
    isSunk = true;
    console.log('INSIDE: ' + isSunk)
  }
  console.log('AFTER: ' + isSunk)
  return {
    isSunk: () => isSunk,
    hitLocation,
    hits,
    shipSize
  }
}

const two = ships(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk())

Other option is to use a class.

class Ship {

    hits = [];
    
    constructor(length) {
        this.shipSize = length;
    }
    
    get isSunk() {
        return this.hits.length === this.shipSize;
    }
    
    hitLocation (location) {
      this.hits.push(location);
      console.log('INSIDE: ' + this.isSunk)
    }
    
}


const two = new Ship(2)
two.hitLocation(1)
two.hitLocation(2)
console.log('FINAL: ' + two.isSunk)