js code to retrieve the format of any given image (square, horizontal, vertical) *jquery free*

get-img-format.js

function getAspectRatio(img) {
    return img.width / img.height;
}

function getImgFormat(img) {
    var aspectRatio = getAspectRatio(img);

    if(aspectRatio === 1) {
        return 'square';
    } else if (aspectRatio > 1) {
        return 'horizontal';
    } else {
        return 'vertical';
    }
}

// usage
var myImg = document.getElementById('myImg');
getImgFormat(myImg);