add comments with transition flow details

Author: yyx990803

src/transition/transition.js

@@ -48,6 +48,24 @@ var p = Transition.prototype
 /**
  * Start an entering transition.
  *
+ * 1. enter transition triggered
+ * 2. call beforeEnter hook
+ * 3. add enter class
+ * 4. insert/show element
+ * 5. call enter hook (with possible explicit js callback)
+ * 6. reflow
+ * 7. based on transition type:
+ *    - transition:
+ *        remove class now, wait for transitionend,
+ *        then done if there's no explicit js callback.
+ *    - animation:
+ *        wait for animationend, remove class,
+ *        then done if there's no explicit js callback.
+ *    - no css transition:
+ *        done now if there's no explicit js callback.
+ * 8. wait for either done or js callback, then call
+ *    afterEnter hook.
+ *
  * @param {Function} op - insert/show the element
  * @param {Function} [cb]
  */
@@ -96,6 +114,20 @@ p.enterDone = function () {
 /**
  * Start a leaving transition.
  *
+ * 1. leave transition triggered.
+ * 2. call beforeLeave hook
+ * 3. add leave class (trigger css transition)
+ * 4. call leave hook (with possible explicit js callback)
+ * 5. reflow if no explicit js callback is provided
+ * 6. based on transition type:
+ *    - transition or animation:
+ *        wait for end event, remove class, then done if
+ *        there's no explicit js callback.
+ *    - no css transition: 
+ *        done if there's no explicit js callback.
+ * 7. wait for either done or js callback, then call
+ *    afterLeave hook.
+ *
  * @param {Function} op - remove/hide the element
  * @param {Function} [cb]
  */