JSFiddle - React, Tailwind, and code Playground

JavaScript

function sumMultiplesOfTwoOrThree(n){
    var sum= 0;
    for (var i=1;i<n;i++) {
        if (((i % 3) === 0) || ((i % 5) === 0)) {
            sum += i;
        }
    }
    return sum;
}
console.log(sumMultiplesOfTwoAndThree(1000))