Poisson distribution formula in javascript

poissonDistribution.js

var k_total = 10; // number of times the event is repeated
var landa = 8;  // Promedian number of error expected in a given time (Landa symbol)
var exponential = 2.718281828;
var total = 0;
var numerator, denominator;

// Sumatorio de k terminos usando la formula de poisson

function poisson(k, landa) {
    exponentialPower = Math.pow(exponential, -landa); // negative power k
    landaPowerK = Math.pow(landa, k); // Landa elevated k
    numerator = exponentialPower * landaPowerK;
    denominator = fact(k); // factorial of k.
    
    return (numerator / denominator);
}

for (var i = 0; i < k_total; i++) {
    total += poisson(i, landa);
}

console.log("Total sum is " + total);

function fact(x) {
   if(x==0) {
      return 1;
   }
   return x * fact(x-1);
}

thanks for share your code. This has helped me a lot.