JavaScript – Child objects called by functions to update child objects

I am learning about objects and their scopes, I got confused and decided to make a D&D pathfinder character sheet for practice.

I made the character sheet as an object, child objects for ability scores, strength/dexterity/intelligence/etc… and then base and modifier values.

in D&D you use your base value to calculate your modifier value and the modifier is used throughout the game. The calculation for modifier is (base - 10) / 2

as i run this i only get 0 when called console.log(characterSheet.abilityScore.strength.modifier)

I assume my confusion is about my understanding of the scope range between the function and modifier/base. but I’m not sure where to start.

const characterSheet = {
  abilityScore: {
    strength: {
      base: 2,
      modifier: 0,
      calcMod: function () {
        this.modifier = Math.floor((this.base - 10) / 2);
      },
    },
    dexterity: {
      base: 8,
      modifier: 0,
      calcMod: function () {
        this.modifier = Math.floor((this.base - 10) / 2);
      },
    },
    intelligence: {
      base: 16,
      modifier: 0,
      calcMod: function () {
        this.modifier = Math.floor((this.base - 10) / 2);
      },
    },
  },
}

I have also tried placing the function in the global scope but always returns NaN.

const characterSheet = {
  abilityScore: {
    strength: {
      base: 2,
      modifier: function () {
        return calcMod(this.base);
      },
    strength: {
      base: 8,
      modifier: function () {
        return calcMod(this.base);
      },
    },
    strength: {
      base: 16,
      modifier: function () {
        return calcMod(this.base);
      },
    },
  },
}};
function calcMod(val) {
  return Math.floor((val - 10) / 2);
}

console.log(calcMod(characterSheet.abilityScore.strength));

Answer

you can use that… ?

const characterSheet =
  { abilityScore: 
    { strength:
      { base      : 2
      , modifier  : 0
      }
    , dexterity: 
      { base      : 8
      , modifier  : 0
      }
    , intelligence: 
      { base      : 16
      , modifier  : 0
      }
    , calcMod ( ability )
      { 
      return this[ability].modifier = 0 | ((this[ability].base - 10) / 2);       
  } } } 

console.log( characterSheet.abilityScore.calcMod( 'strength' ) )

console.log( characterSheet.abilityScore.strength.modifier )

OR:

const characterSheet =
  { abilityScore: 
    { strength     : { base :  2, modifier : 0 }
    , dexterity    : { base :  8, modifier : 0 }
    , intelligence : { base : 16, modifier : 0 }
  } };
  
function calcMod( val ) 
  {
  return val.modifier = 0 | ((val.base - 10) / 2);
  }

console.log( calcMod( characterSheet.abilityScore.strength ))