Method updateMixins

src/core/a-node.js:189–233

* Unregister old mixins and listeners. * Register new mixins and listeners. * Registering means to update `this.mixinEls` with listeners.

(newMixins, oldMixins)

   * Registering means to update `this.mixinEls` with listeners.
   */
  updateMixins (newMixins, oldMixins) {
    var newMixinIdArray = ANode.newMixinIdArray;
    var oldMixinIdArray = ANode.oldMixinIdArray;
    var mixinIds = ANode.mixinIds;

    var i;
    var newMixinIds;
    var oldMixinIds;

    newMixinIdArray.length = 0;
    oldMixinIdArray.length = 0;
    newMixinIds = newMixins ? utils.split(newMixins.trim(), /\s+/) : newMixinIdArray;
    oldMixinIds = oldMixins ? utils.split(oldMixins.trim(), /\s+/) : oldMixinIdArray;

    mixinIds.newMixinIds = newMixinIds;
    mixinIds.oldMixinIds = oldMixinIds;

    // Unregister old mixins.
    for (i = 0; i < oldMixinIds.length; i++) {
      if (newMixinIds.indexOf(oldMixinIds[i]) === -1) {
        this.unregisterMixin(oldMixinIds[i]);
      }
    }

    // Register new mixins.
    this.computedMixinStr = '';
    this.mixinEls.length = 0;
    for (i = 0; i < newMixinIds.length; i++) {
      this.registerMixin(newMixinIds[i]);
    }

    // Update DOM. Keep track of `computedMixinStr` to not recurse back here after
    // update.
    if (this.computedMixinStr) {
      this.computedMixinStr = this.computedMixinStr.trim();
      window.HTMLElement.prototype.setAttribute.call(this, 'mixin',
                                                     this.computedMixinStr);
    }

    if (newMixinIds.length === 0) {
      window.HTMLElement.prototype.removeAttribute.call(this, 'mixin');
    }

    return mixinIds;
  }

  /**
   * From mixin id, add mixin element to `mixinEls`.