feat(joinFilter): add a filter to join collections into a string

README.md

@@ -26,6 +26,7 @@
   - [fuzzyBy](#fuzzyby)
   - [groupBy](#groupby)
   - [isEmpty](#isempty)
+  - [join] (#join)
   - [last](#last)
   - [map](#map)
   - [omit](#omit)
@@ -341,6 +342,25 @@ $scope.weirdArray = [[], 1, 2, 3, [4, 5, 6, [7, 8, 9, [10, 11, [12, [[[[[13], [[
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
 ```
 
+### join
+Joins the contents of a collection into a string.<br/>
+By default, it will join elements with a *single space*, but you can provide your own delimiter.
+
+**Usage:** ```collection | join:', '```
+
+Example:
+
+```js
+$scope.names = ['John', 'Sebastian', 'Will', 'James'];
+```
+
+```html
+<p>{{ names | join:', ' }}</p>
+<!-- Will print "John, Sebastian, Will, James" -->
+
+```
+
+
 ###fuzzy
 fuzzy string searching(approximate string matching). [Read more](http://en.wikipedia.org/wiki/Approximate_string_matching)<br/>
 **note:** use fuzzyBy to filter by one property to improve performance<br/>

src/_filter/collection/join.js

@@ -0,0 +1,23 @@
+/**
+ * @ngdoc filter
+ * @name join
+ * @kind function
+ *
+ * @description
+ * join a collection by a provided delimiter (space by default)
+ */
+angular.module('a8m.join', [])
+  .filter('join', function () {
+    'use strict';
+    return function (input, delimiter) {
+      if (isUndefined(input) || !isArray(input)) {
+        return input;
+      }
+      if (!delimiter) {
+        delimiter = ' ';
+      }
+
+      return input.join(delimiter);
+    };
+  })
+;

src/filters.js

@@ -50,6 +50,7 @@ angular.module('angular.filter', [
   'a8m.first',
   'a8m.last',
   'a8m.flatten',
+  'a8m.join',
 
   'a8m.math',
   'a8m.math.max',

test/spec/filter/collection/join.js

@@ -0,0 +1,78 @@
+'use strict';
+
+describe('isJoinFilter', function () {
+  var joinFilter;
+
+  beforeEach(module('a8m.join'));
+
+  beforeEach(inject(function (_joinFilter_) {
+    joinFilter = _joinFilter_;
+  }));
+
+  describe('given a collection', function () {
+    var arr;
+
+    describe('which is empty', function () {
+      beforeEach(function () {
+        arr = [];
+      });
+
+      it('should return an empty string', function () {
+        expect(joinFilter(arr)).toEqual('');
+      });
+
+    });
+
+    describe('of strings', function () {
+      beforeEach(function () {
+        arr = ['hello', 'world'];
+      });
+
+      describe('with no delimiter', function () {
+        it('should join elements with a space', function () {
+          expect(joinFilter(arr)).toEqual('hello world');
+        });
+      });
+
+      describe('with a custom delimiter', function () {
+        var delim;
+
+        describe('which is not a string', function () {
+          it('should join elements with a toString representation of the delimiter', function () {
+            delim = true;
+            expect(joinFilter(arr, delim)).toEqual('hellotrueworld');
+
+            delim = 10;
+            expect(joinFilter(arr, delim)).toEqual('hello10world');
+
+            delim = {toString: function () { return ' - ' }}
+            expect(joinFilter(arr, delim)).toEqual('hello - world');
+          });
+        });
+
+        it('should join elements with the given delimiter', function () {
+          delim = ', '
+          expect(joinFilter(arr, delim)).toEqual('hello, world');
+        });
+      });
+    });
+
+  });
+
+  describe('given something that is not a collection', function () {
+    var str, obj, bool, num;
+    beforeEach(function () {
+      str = 'string';
+      obj = {'a': 'b'};
+      bool = true;
+      num = 5;
+    });
+
+    it('should return the input as is', function () {
+      expect(joinFilter(str)).toEqual(str);
+      expect(joinFilter(obj)).toEqual(obj);
+      expect(joinFilter(bool)).toEqual(bool);
+      expect(joinFilter(num)).toEqual(num);
+    });
+  });
+});