Search code examples
javascriptqualtrics

Image randomization in qualtrics

I'm creating a qualtrics survey and I'd like to create a way to randomize which images participants will see on a given questions

Here's the basic code I have so far

var banner = document.getElementById('banner');
var picture = document.getElementById('picture');

banner.style.display = 'none';
picture.style.display = 'none';

images = [banner, picture];

function randomImage() {
    var idx = Math.floor(Math.random(0, images.length - 1) * 10);

    return images[idx];
};

var image1 = randomImage(); 
image1.style.display = 'block';

Where 'picture' and 'banner' are the ids of two images. However, this doesn't seem to work, the images disappear but a random image does not reappear. Any advice on a better way to make this function?

Solution

  • Should be...

    var idx = Math.floor(Math.random() * images.length);

    ... as at the moment you for some reason multiply the result by 10, having quite a low chance for the final result to be either 0 or 1.

    Note that Math.random() doesn't take any arguments: it always generates a number in [0, 1) range.