Function updateClass

static/vuejs/vue.runtime.esm.js:5308–5330

(oldVnode, vnode)

/*  */

function updateClass (oldVnode, vnode) {
  var el = vnode.elm;
  var data = vnode.data;
  var oldData = oldVnode.data;
  if (!data.staticClass && !data.class &&
      (!oldData || (!oldData.staticClass && !oldData.class))) {
    return
  }

  var cls = genClassForVnode(vnode);

  // handle transition classes
  var transitionClass = el._transitionClasses;
  if (transitionClass) {
    cls = concat(cls, stringifyClass(transitionClass));
  }

  // set the class
  if (cls !== el._prevClass) {
    el.setAttribute('class', cls);
    el._prevClass = cls;
  }
}

var klass = {
  create: updateClass,