set css for each repeated section JS

gistfile1.txt

_.map(document.querySelectorAll('.challenge'), function(element) {
  var position;
  position = element.getAttribute('data-position');
  // determine direction of slide and apply styles
  if(position > scope.index){ // slide right
    element.classList.add('right');
    element.setAttribute('style', 'display:block; width:' + avgWidth + 'px; float:left;');
  }
  if(position < scope.index) { // slide left
    element.classList.add('left');
    element.setAttribute('style', 'display:block; width:' + avgWidth + 'px; float:right;');
  }
  if(position === scope.index) { // expand center
    element.setAttribute('style', 'display:block; width:' + avgWidth + 'px; float:left; background-image:linear-gradient(rgba(0, 0, 0, 0.0),rgba(0, 0, 0, .25)), url(images/challenges/hero-background.png), url(images/challenges/'+scope.challenge.attributes.image+'); background-repeat:no-repeat; background-size: cover; background-origin:border-box');
    element.querySelector('.content').style.display = 'none'; // hide inner content
  }
});