Add getNeighbours method

Author: tillarnold

lib/fixed-2d-array.js

@@ -42,4 +42,41 @@ Fixed2DArray.prototype.set = function(x,y,val) {
   this._grid[x][y] = val;
 };
 
+/**
+ * Returns all neighbours of the given coordinate.
+ *
+ * For example: 
+ * [ ][ ][ ][ ][ ]
+ * [ ][*][*][*][ ]
+ * [ ][*][X][*][ ]
+ * [ ][*][*][*][ ]
+ * [ ][ ][ ][ ][ ]
+ *
+ * the given coordinates are marked with an `X`
+ * the function will return an array containing
+ * the values for the fields maked with an `*` 
+ */
+Fixed2DArray.prototype.getNeighbours = function(x,y){
+  this.validateCoords(x,y);
+  
+  var returnArray = [];
+
+  for(var i=x-1; i<=x+1; i++){
+    for(var j=y-1; j<=y+1; j++){
+      try {
+        if(!(i===x && j===y)) {
+          var element = this.get(i,j);
+          returnArray.push(element);
+          console.log('added',i,j);
+        }
+      }
+      catch(e) {
+        //this is a field at the edge of the grid.
+        //ignore
+      }
+    }
+  }
+  return returnArray;
+};
+
 module.exports = Fixed2DArray;

test/test.js

@@ -16,8 +16,18 @@ test('get and set', function (t) {
 });
 
 test('exception on index out of bounds', function (t) {
-  t.plan(2);
+  t.plan(3);
   var fa = new fixedArray(10,10);
   t.throws(function(){fa.get(10,10);});
   t.throws(function(){fa.get(-1,-1);});
+  t.throws(function(){fa.getNeighbours(-1,-1);});
 });
+
+test('get correct number of neighbours',function (t) {
+  t.plan(3); 
+  var fa = new fixedArray(10,10);
+  t.equal(fa.getNeighbours(5,5).length,8);
+  t.equal(fa.getNeighbours(0,0).length,3);
+  t.equal(fa.getNeighbours(1,0).length,5);
+});
+