Adds _.rchop (with README, tests)

README.markdown

@@ -116,6 +116,13 @@ _.chop('whitespace', 3)
 => ['whi','tes','pac','e']
 ```
 
+**rchop** _.rchop(string, step)
+
+```javascript
+_.rchop('whitespace', 3)
+=> ['w', 'hit', 'esp', 'ace']
+```
+
 **clean** _.clean(str)
 
 Compress some whitespaces to one.

lib/underscore.string.js

@@ -213,6 +213,13 @@
       return step > 0 ? str.match(new RegExp('.{1,' + step + '}', 'g')) : [str];
     },
 
+    rchop: function(str, step){
+      if (str == null) return [];
+      str = String(str);
+      step = ~~step;
+      return step > 0 ? str.match(new RegExp('(.{1,' + step + '})(?=(?:.{' + step + '})*$)', 'g')) : [str];
+    },
+
     clean: function(str){
       return _s.strip(str).replace(/\s+/g, ' ');
     },
@@ -641,6 +648,7 @@
 
   // Aliases
 
+  _s.lchop    = _s.chop;
   _s.strip    = _s.trim;
   _s.lstrip   = _s.ltrim;
   _s.rstrip   = _s.rtrim;

test/speed.js

@@ -59,11 +59,11 @@
   });
 
   JSLitmus.test('succ', function(){
-    var let = 'a', alphabet = [];
+    var ch = 'a', alphabet = [];
 
     for (var i=0; i < 26; i++) {
-        alphabet.push(let);
-        let = _(let).succ();
+        alphabet.push(ch);
+        ch = _(ch).succ();
     }
 
     return alphabet;

test/strings.js

@@ -192,6 +192,17 @@ $(document).ready(function() {
     ok(_(12345).chop(1).length === 5, 'output [1, 2, 3,  4, 5]');
   });
 
+  test('String: rchop', function(){
+    ok(_('whitespace').rchop(2).length === 5, 'output [wh, it, es, pa, ce]');
+    ok(_('whitespace').rchop(3).length === 4, 'output [w, hit, esp, ace]');
+    ok(_('whitespace').rchop()[0].length === 10, 'output [whitespace]');
+    ok(_('whitespace').rchop(-1)[0].length === 10, 'output [whitespace]');
+    ok(_('whitespace').rchop(NaN)[0].length === 10, 'output [whitespace]');
+    ok(_('whitespace').rchop(null)[0].length === 10, 'output [whitespace]');
+    ok(_('whitespace').rchop({})[0].length === 10, 'output [whitespace]');
+    ok(_(12345).rchop(1).length === 5, 'output [1, 2, 3, 4, 5]');
+  });
+
   test('String: clean', function(){
     equal(_.clean(' foo     bar   '), 'foo bar');
     equal(_.clean(''), '');