WPML custom icons : how to change their CSS according to active language/url.

//set a location variable to contain the pathname of your URL
var loc = window.location.pathname;

//gain access to the appropriate elements in the DOM
var myDutchLink = document.getElementById('insert-your-element-here');
var myFrenchLink = document.getElementById('insert-your-element-here');

//create a conditional to check if the 'nl' Dutch designator is found in your pathname, and style your links accordingly
if(loc.indexOf('nl') != -1) {
    //style your links here if 'nl' IS found in the pathname of the url, either via checking then adding and removing styled classes, or styling the elements directly
} else {
    //style your links if 'nl' is NOT found in the pathname of the url, either via checking then adding and removing styled classes, or styling the elements directly
}