Get a random element for an array based on different probabilities?

Question

Well, imagine I'm creating a Pokemon game in JavaScript. I have such an object ...

pokemon = { "pikachu": {hp: 100, probability: 0.1}, "squirtle": {hp: 90, probability: 0.2} }; 

I basically need a function to select Pokémon in an object at random, but also based on probability. Thus, in this case, the functions are more likely to select "squirtle", since the probability is higher than "pikachu".

Answer 1

I would go through the pokemon array and summarize all the probabilities. Call it total

Then create a value from 0 to total . Call it randVal

Then scroll, adding probabilities again. Call it secondTotal
The first pokemon, the probability of which clicks secondTotal above randVal , is your chosen pokemon.

Answer 2

 function pickAWinningItem(data) { var winner = Math.random(); var threshold = 0; for (let i = 0; i < data.length; i++) { threshold += parseFloat(data[i].prob); if (threshold > winner) { return data[i] } } } 

The sum of all the probabilities should be 1. Using this function, you add probabilities on top of each other and return the element that a random number is the range of its probability.