main.js

var main = function (highlight = true) {

    const getRandomColor = function (alpha = '') {
        const randomColor = Math.floor(Math.random() * 16777215).toString(16);
        return "#" + randomColor + alpha;
    }

    const divs = document.getElementsByTagName('div');
    const divsInitial = [];
    if (divsInitial.length <= 0) {
        for (let i = 0; i < divs.length; i++) {
            divsInitial[i] = divs[i];
        }
    }

    const changeDivColor = function () {
        for (let i = 0; i < divs.length; i++) {
            const randomColor = getRandomColor();
            divs[i].style.backgroundColor = randomColor + '88';
            divs[i].style.border = 'solid ' + randomColor + 'ff';
        }
    }
    if (highlight) { changeDivColor(); }

    const restoreDivColor = function () {
        for (let i = 0; i < divs.length; i++) {
            divs[i].style.backgroundColor = divsInitial[i].style.backgroundColor ? divsInitial[i].style.backgroundColor : '';
            divs[i].style.border = divsInitial[i].style.border ? divsInitial[i].style.border : '';
        }
    }
    if (!highlight) { restoreDivColor(); }

}
main();