Merge pull request #45 from wetheredge/master

Get tabs by position

README.md

@@ -88,7 +88,31 @@ Add a new tab to the tab group and returns a `Tab` instance.
 
 #### `tabGroup.getTab(id)`
 
-Retrieve an instance of `Tab` from its `id` (return `null` if not found).
+Retrieve an instance of `Tab` from this `id` (return `null` if not found).
+
+#### `tabGroup.getTabByPosition(position)`
+
+Retrieve an instance of `Tab` from this `position` (return `null` if not found). A negative value is an offset from the right.
+
+To get the tab in the leftmost position:
+
+```javascript
+tabGroup.getTabByPosition(1);
+```
+
+To get the tab in the rightmost position:
+
+```javascript
+tabGroup.getTabByPosition(-1);
+```
+
+> Note: Position 0 does not contain a tab.
+
+#### `tabGroup.getTabByRelPosition(position)`
+
+Retrieve an instance of `Tab` from this `position` relative to the active tab (return `null` if not found).
+`tabGroup.getNextTab()` is an alias to `tabGroup.getTabByRelPosition(1)`.
+`tabGroup.getPreviousTab()` is an alias to `tabGroup.getTabByRelPosition(-1)`.
 
 #### `tabGroup.getActiveTab()`
 
@@ -138,21 +162,7 @@ Get current tab icon URL / icon.
 
 #### `tab.setPosition(newPosition)`
 
-Move tab to the specified position. A negative value is an offset from the right.
-
-To move a tab to the leftmost position:
-
-```javascript
-tab.setPosition(1);
-```
-
-> Note: a position of 0 also moves the tab to the leftmost position
-
-To move a tab to the rightmost position:
-
-```javascript
-tab.setPosition(-1);
-```
+Move tab to the specified position. If `position` is 0 then `null` is returned and nothing happens. See [`tabGroup.getTabByPosition`](#tabgroupgettabbypositionposition) for information about positions.
 
 #### `tab.getPosition(fromRight)`
 

index.js

@@ -76,6 +76,32 @@ class TabGroup extends EventEmitter {
         return null;
     }
 
+    getTabByPosition (position) {
+        let fromRight = position < 0;
+        for (let i in this.tabs) {
+            if (this.tabs[i].getPosition(fromRight) === position) {
+                return this.tabs[i];
+            }
+        }
+        return null;
+    }
+
+    getTabByRelPosition (position) {
+        position = this.getActiveTab().getPosition() + position;
+        if (position <= 0) {
+            return null;
+        }
+        return this.getTabByPosition(position);
+    }
+
+    getNextTab () {
+        return this.getTabByRelPosition(1);
+    }
+
+    getPreviousTab () {
+        return this.getTabByRelPosition(-1);
+    }
+
     getTabs () {
       return this.tabs;
     }
@@ -212,7 +238,7 @@ class Tab extends EventEmitter {
     setPosition (newPosition) {
         let tabContainer = this.tabGroup.tabContainer;
         let tabs = tabContainer.children;
-        let oldPosition = this.getPosition();
+        let oldPosition = this.getPosition() - 1;
 
         if (newPosition < 0) {
             newPosition += tabContainer.childElementCount;
@@ -247,8 +273,8 @@ class Tab extends EventEmitter {
             position -= this.tabGroup.tabContainer.childElementCount;
         }
 
-        if (position === 0) {
-            position = 1;
+        if (position >= 0) {
+            position++;
         }
 
         return position;