I don’t how why my backgroundImage doesn’t work

Why does my banner doesn’t change her background? Please help me.

When I run the file the console tells me:

Uncaught TypeError: flechedroite.addEventListener is not a function

I really don’t understand. I’m a beginner in Javascript so please explain me with kind words how I can fix this error 🙂

var flechedroite = document.getElementsByClassName('fa-arrow-right');
var flechegauche = document.getElementsByClassName('switch-left');
var banner = document.getElementById('banner');
var images = [];

var changeBackground = function (bElement, bUrl) {
    return bElement.style.backgroundImage = "url(" + bUrl + ")";
}

//image list
images[0] = 'images/image1.jpg';
images[1] = 'images/image2.jpg';
images[2] = 'images/image3.jpg';

flechedroite.addEventListener('click', function() {
    for (var i = 0; i < images.length; i++) {
        changeBackground(document.body, images[i]);
    }
})

Answer

1. addEventListener should be called in window.onload or in $(document).ready()
2. Since getElementsByClassName returns an array, you need to use array index with flechedroite to add an event listener. i.e. flechedroite[0].addEventListener(‘click’, function() {…});
3. You are calling changeBackground function in a loop to set the background image, effectively you will see only the last image from the array being set as background.

JS Code

var  images = [];

var changeBackground = function (bElement, bUrl) {
    return bElement.style.backgroundImage = "url("+bUrl+")";
}

//image list
images[0] = 'https://www.gettyimages.ie/gi-resources/images/Homepage/Hero/UK/CMS_Creative_164657191_Kingfisher.jpg';
images[1] = 'https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTOGUhZo0Qe81U5qY_Z-seXgsD79LEEet832TVOlLMOEy10ZPsV';
images[2] = 'https://cdn.pixabay.com/photo/2016/06/18/17/42/image-1465348_960_720.jpg';


window.onload = function(){
    var flechedroite = document.getElementsByClassName('fa-arrow-right');
    var flechegauche = document.getElementsByClassName('switch-left');
    var banner = document.getElementById('banner');
    var currentImageIndex = 0;
    flechedroite[0].addEventListener('click', function() {
        currentImageIndex = (currentImageIndex+1)%images.length;
        changeBackground(document.body, images[currentImageIndex]);
    })
}