JavaScript: count from Int to Int in X amount of time

javascript.js

// This function counts the integers/strings only containing numbers to the target integer
function animateValue(className, start, end, duration) {

    // Get target element
    var obj = document.getElementById(className);
  
    // Set range
    var range = end - start;
  
    // Set minimum timer. Shorter than 50ms is not really visible any way
    var minTimer = 50;
  
    // Calculate step value
    var stepTime = Math.abs(Math.floor(duration / range));

    // Limit function to never go below minTimer
    stepTime = Math.max(stepTime, minTimer);

    // Get current dateTime
    var startTime = new Date().getTime();
  
    // Set end dateTime
    var endTime = startTime + duration;
    var timer;

    // Run timing function on calculated interval
    function run() {
        var now = new Date().getTime();
        var remaining = Math.max((endTime - now) / duration, 0);
        var value = Math.round(end - (remaining * range));
        obj.innerHTML = value;
        if (value == end) {
            clearInterval(timer);
        }
    }

    timer = setInterval(run, stepTime);
    run();
}

// ======== SINGLE ELEMENT EXAMPLE ======== //
// Example is set for 5 seconds.

animateValue('#element', 0, 1000, 5000);

// OR

// Get the element
var element = document.getElementById('#element');

// Get the target value
var element = element.getAttribute('data-target');

// Set duration (5 seconds)
var duration = 5000;

animateValue( element, 0, target, duration);


// ======== MULTIPLE ELEMENT EXAMPLE ======== //
// Example is set for 10 seconds.

// Get all target elements
var elements = document.querySelectorAll('.classname');

// For each element, assign animation
elements.forEach(element => {

    // Get target value
    var targetValue = element.getAttribute('data-target');
  
    // Get element ID, important
    var elementID = element.getAttribute('id');

    // Run function
    animateValue(elementID, 0, targetValue, 10000);
});