JSFiddle - React, Tailwind, and code Playground

by Riivr

HTML

<input id="answer" />

JavaScript

var number = 3

function multiplesOf3and5(number) {

  var numberArray = [];
  var total = 0;

  for(var i=1; i <= number; i++){
    if(i % 5 == 0) {
      numberArray.push(i);      
    } else if (i % 3 == 0) {
      numberArray.push(i);
    }
  }

  for(var num in numberArray) {
    total += num;
  }

  return total;
}

var test = multiplesOf3and5(number);

$("#answer").val(test);