Moving Dom elements

/* Create a module that works with moving div elements. Implement functionality for:
Add new moving div element to the DOM
The module should generate random background, font and border colors
All the div elements are with the same width and height
The movements of the div elements can be either circular or rectangular
The elements should be moving all the time */

'use strict';

(function () {
    document.getElementById("run-button").addEventListener("click", run);

    function run() {

        // Clear old divs
        var oldDivs = document.getElementsByTagName('div');
        while (oldDivs.length > 0) {
            oldDivs[0].parentNode.removeChild(oldDivs[0]);
        }
        // Clear all old window.setInterval-s
        var interval_id = window.setInterval("", 9999);
        for (var i = 1; i < interval_id; i++) {
            window.clearInterval(i);
        }

        var documentFragment = document.createDocumentFragment();
        // DivCount best performance with 20;
        var divCount = 20;
        for (var i = 0; i < divCount; i++) {
            if (getRandomMoveType() === 1) {
                var div = module.createDiv("rectangular");
                documentFragment.appendChild(div);
                module.moveRectanglePath(div);
            } else {
                var div = module.createDiv("circle");
                documentFragment.appendChild(div);
                module.moveCirclePath(div);
            }
        }
        document.body.appendChild(documentFragment);
    }

    function getRandomMoveType() {
        var random = Math.floor(Math.random() * 2);
        return random;
    }
}());

var module = (function () {

    // Public functions
    return {
        createDiv: function (kind) {
            var element = document.createElement('div');
            element.kind = kind;
            element.style.width = "50px";
            element.style.height = "50px";
            element.style.position = "absolute";
            element.style.top = getRandomPositionTop() + "px";
            element.style.left = getRandomPositionLeft() + "px";
            element.style.backgroundColor = getRandomColor();
            element.innerHTML = "div";
            element.style.fontSize = "30px";
            element.style.color = getRandomColor();
            element.style.border = "5px solid " + getRandomColor();
            // Save initial position
            element.initialTop = parseInt(element.style.top);
            element.initialLeft = parseInt(element.style.left);

            return element;

            function getRandomColor() {
                var r = getRandomNumber(0, 255);
                var g = getRandomNumber(0, 255);
                var b = getRandomNumber(0, 255);

                return "rgb(" + r + ", " + g + ", " + b + " )";
            }

            function getRandomPositionTop() {
                return getRandomNumber(100, screen.height - 100);
            }

            function getRandomPositionLeft() {
                return getRandomNumber(100, screen.width - 100);
            }
        },
        moveRectanglePath: function (div) {
            var self = div;
            var width = getRandomNumber(100, 200);
            var height = getRandomNumber(100, 200);
            window.setInterval(function () {
                    var div = self;
                    var left = parseInt(div.style.left);
                    var startLeft = div.initialLeft;
                    var top = parseInt(div.style.top)
                    var startTop = div.initialTop;

                    // left
                    if (top === startTop && left < startLeft + height) {
                        left++;
                        div.style.left = left + "px";
                    }
                    // down
                    if (left === startLeft + height && top < startTop + width) {
                        top++;
                        div.style.top = top + "px";
                    }
                    // right
                    if (top === startTop + width && left > startLeft) {
                        left--;
                        div.style.left = left + "px";
                    }
                    // up
                    if (left === startLeft && top > startTop) {
                        top--;
                        div.style.top = top + "px";
                    }
            }, getRandomNumber(10, 200), self, width, height);
        },
        moveCirclePath: function (div) {
            var angleInDegrees = 0;
            var self = div;
            var radius = getRandomNumber(100, 200);

            window.setInterval(function () {
                angleInDegrees++;
                if (angleInDegrees === 360) {
                    angleInDegrees = 0;
                }

                var div = self;
                var centerLeft = div.initialLeft;
                var centerTop = div.initialTop;

                if (angleInDegrees > 360) {
                    angleInDegrees = 0;
                }

                var angleInRadians = angleInDegrees * Math.PI / 180.0;
                div.style.top = (radius * Math.cos(angleInRadians) + centerTop) + "px";
                div.style.left = (radius * Math.sin(angleInRadians) + centerLeft) + "px";

            }, getRandomNumber(10,500), self, angleInDegrees, radius);
        },
    }
    // Private function
    function getRandomNumber(start, end) {
        var random = Math.floor((Math.random() * (end - start) + start));
        return random;
    }
}());