Added callback

README.md

@@ -13,23 +13,26 @@ var el = document.querySelector('#el');
 fade.out(el); // fade el out in 1s
 fade.in(el, 1500); // fade el in in 1.5s
 fade(el, 0.3, 3000); // fade el to opacity 0.3 in 3s 
+fade.out(el, function() {
+  el.style.display = 'none'; // set display to none after fade out
+});
 ```
 
 ## API
 
 The default `duration` always is `1000` ms.
 
-### fade(el, opacity[, duration])
+### fade(el, opacity[, duration][, callback])
 
-Fade `el` to `opacity` (in `duration` ms).
+Fade `el` to `opacity` (in `duration` ms). Call `callback` when finished.
 
-### fade.out(el[, duration])
+### fade.out(el[, duration][, callback])
 
-Fade out `el` (in `duration` ms).
+Fade out `el` (in `duration` ms). Call `callback` when finished.
 
-### fade.in(el[, duration])
+### fade.in(el[, duration][, callback])
 
-Fade in `el` (in `duration` ms).
+Fade in `el` (in `duration` ms). Call `callback` when finished.
 
 ## Installation
 
@@ -63,4 +66,4 @@ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+SOFTWARE.

index.js

@@ -16,20 +16,26 @@ module.exports = fade;
  * @param {Element} el
  * @param {Number} opacity
  * @param {Number=} duration
+ * @param {Function=} callback
  *
  * @todo Add other vendor prefixes
  * @todo Properly clear transition
  */
 
-function fade (el, opacity, duration) {
+function fade (el, opacity, duration, callback) {
   if (typeof duration === 'undefined') duration = 1000;
+  else if (typeof duration === 'function') {
+    callback = duration;
+    duration = 1000;
+  }
 
   var oldTransition = prefixed.get(el.style, 'transition') || '';
   prefixed(el.style, 'transition', 'opacity ' + (duration/1000) + 's');
   el.style.opacity = opacity;
 
   setTimeout(function () {
     prefixed(el.style, 'transition', oldTransition);
+    if (callback) callback();
   }, duration);
 }
 
@@ -38,19 +44,21 @@ function fade (el, opacity, duration) {
  *
  * @param {Element} el
  * @param {Number=} duration
+ * @param {Function=} callback
  */
 
-fade.out = function (el, duration) {
-  fade(el, 0, duration);
+fade.out = function (el, duration, callback) {
+  fade(el, 0, duration, callback);
 };
 
 /**
  * Fade out `el`.
  *
  * @param {Element} el
  * @param {Number=} duration
+ * @param {Function=} callback
  */
 
-fade['in'] = function (el, duration) {
-  fade(el, 1, duration);
+fade['in'] = function (el, duration, callback) {
+  fade(el, 1, duration, callback);
 };