Generate random integers with probabilities

Question

I\'m a bit confused about how to generate integer values with probabilities.

As an example, I have four integers with their probability values: 1|0.4, 2|0.3, 3|0.2,

Answer 1

This is the solution i find the most flexible, for picking within any set of object with probabilities:

// set of object with probabilities:
const set = {1:0.4,2:0.3,3:0.2,4:0.1};

// get probabilities sum:
var sum = 0;
for(let j in set){
    sum += set[j];
}

// choose random integers:
console.log(pick_random());

function pick_random(){
    var pick = Math.random()*sum;
    for(let j in set){
        pick -= set[j];
        if(pick <= 0){
            return j;
        }
    }
}