CODEWITHSUNDEEP
javascriptgame-development
Gaiadok
Gaiadok

Reputation: 45

How do I incorporate Math.random based off of the percentage of a value?

I want to add a random modifier to this code, something that will either add to or subtract from the damage based off of a range of +-20% of the base value. The damage would randomize between a range of 80% of result to 120% of result. For a numeric example:

attacker.Strength(20) - defender.Defense(10) = result

20 - 10 = range(8 to 12)

var Fight = function (attacker, defender) {
    var result;
    result = (attacker.Strength - defender.Defense);
    defender.HP = defender.HP - result;

    if(defender.HP >= 1) {
         return defender.Name + " has taken " + result + " damage!";
    } else {
         return defender.Name + " has been slain";
    }
};

Upvotes: 1

Views: 367

Answers (3)

Yogendra Singh
Yogendra Singh

Reputation: 34367

For eaxact +/- 20%, use random to generate two numbers only i.e. 0, 1.

If 0, treat it as + and if 1, treat it as - e.g. below:

   var randomNum = Math.round(Math.random()); //it will return 0 or 1
   if(randomNum ==0){
      //write +20% code here
      result = (attacker.Strength - defender.Defense)*1.2;
   }else{
      //write -20% code here
      result = (attacker.Strength - defender.Defense)*0.8;
   }

EDIT: For range based, its much simpler.

  var factor = 0.8 + Math.random()*0.4;
  result = (attacker.Strength - defender.Defense)*factor ;

Upvotes: 0

Bergi
Bergi

Reputation: 664548

Math.random returns a number between zero and one. Map this to your range from 0.8 to 1.2 with this:

var factor = Math.random() * 0.4 + 0.8;
//                |           |     |
//              [0, 1[        |     |
//                    \      /      |
//                    [0, 0.4[     /
//                         \      /
//                        [0.8, 1,2[
var result = Math.round((attacker.Strength - defender.Defense) * factor);

Not sure whether you want to round somewhere so that your player's health points are always natural numbers. If not, you should change your death condition to defender.HP > 0.

Upvotes: 3

Ry-
Ry-

Reputation: 224932

As in Math.random() * 0.4?

result = (attacker.Strength - defender.Defense) * (0.8 + Math.random() * 0.4);

Upvotes: 1

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