JSFiddle - React, Tailwind, and code Playground

HTML

<input id="logButton" type="button" onclick="sum()" value="Log" />

JavaScript

sum = function(){
    var i, len, delimitedNumbers, numbers, sum;

    delimitedNumbers = "13-2-10-7-3";

    numbers = delimitedNumbers.split('-');
    len = numbers.length;

    sum = 0;
    for(i = 0; i < len; i++)
    {
        sum = sum + parseInt(numbers[i]);
    }

    alert("The sum is: " + sum);
  }