adds .once() and .removeListener(), fixes #663

Readme.md

@@ -318,6 +318,12 @@ Listen for `console.log(...)`, `console.warn(...)`, and `console.error(...)`.
 ###### .on('console', function(type, errorMessage, errorStack))
 This event is triggered if `console.log` is used on the page. But this event is not triggered if the injected javascript code (e.g. via `.evaluate()`) is using `console.log`.
 
+#### .once(event, callback)
+Similar to `.on()`, but captures page events with the callback one time.
+
+#### .removeListener(event, callback)
+Removes a given listener callback for an event.
+
 #### .screenshot([path][, clip])
 Takes a screenshot of the current page. Useful for debugging. The output is always a `png`. Both arguments are optional. If `path` is provided, it saves the image to the disk. Otherwise it returns a `Buffer` of the image data. If `clip` is provided (as [documented here](https://github.com/atom/electron/blob/master/docs/api/browser-window.md#wincapturepagerect-callback)), the image will be clipped to the rectangle.
 

lib/nightmare.js

@@ -348,6 +348,24 @@ Nightmare.prototype.on = function(event, handler) {
   return this;
 };
 
+/**
+ * once
+ */
+
+Nightmare.prototype.once = function(event, handler) {
+  this.child.once(event, handler);
+  return this;
+};
+
+/**
+ * removeEventListener
+ */
+
+Nightmare.prototype.removeListener = function(event, handler) {
+  this.child.removeListener(event, handler);
+  return this;
+};
+
 /**
  * Queue
  */

test/index.js

@@ -1037,7 +1037,7 @@ describe('Nightmare', function () {
     });
   });
 
-  describe('events', function () {
+  describe.only('events', function () {
     var nightmare;
 
     beforeEach(function() {
@@ -1154,6 +1154,43 @@ describe('Nightmare', function () {
       confirm.should.equal('my confirm');
       response.should.equal('hello!');
     });
+
+    it('should only fire once when using once', function*() {
+      var events = 0;
+      nightmare.once('page', function(type, message) {
+        events++;
+      });
+
+      yield nightmare
+        .goto(fixture('events'))
+      events.should.equal(1);
+    });
+
+    it('should remove event listener', function*() {
+      var events = 0;
+      var handler = function(type, message) {
+        if (type === 'alert') {
+          events++;
+        }
+      };
+
+      nightmare.on('page', handler);
+
+      yield nightmare
+        .goto(fixture('events'))
+        .evaluate(function(){
+          alert('alert one');
+        });
+
+      nightmare.removeListener('page', handler);
+
+      yield nightmare
+        .evaluate(function(){
+          alert('alert two');
+        });
+
+      events.should.equal(1);
+    });
   });
 
   describe('options', function () {