allow function argument to html

README.rdoc

@@ -57,6 +57,8 @@ Context and .find calls are equivalent:
   remove(): remove element
 
   html('new html'): set the contents of the element(s)
+  html(function(index, oldhtml){ return ...; }): set the contents of the element(s) from a method
+
   text('new text'): set the text contents of the element(s)
   append, prepend, before, after: like html(), but add html (or a DOM Element or a Zepto object) to element contents (or before/after)
   html(): get first element's .innerHTML

src/zepto.js

@@ -106,7 +106,7 @@ var Zepto = (function() {
     html: function(html){
       return html === undefined ?
         (this.length > 0 ? this.dom[0].innerHTML : null) :
-        this.each(function(){ this.innerHTML = html });
+        this.each(function(idx){ this.innerHTML = typeof html == 'function' ? html(idx, this.innerHTML) : html });
     },
     text: function(text){
       return text === undefined ?

test/zepto.html

@@ -460,6 +460,19 @@ <h1>Zepto DOM unit tests</h1>
         t.assertEqual("", $('#htmltest3').html());
 
         t.assertNull($('doesnotexist').html());
+
+        div.html('yowza');
+        div.html(function(idx, html){
+          return html.toUpperCase();
+        });
+        t.assertEqual('YOWZA', div.html());
+
+        div.html('<u>a</u><u>b</u><u>c</u>');
+
+        $('u').html(function(idx,html){
+          return idx+html;
+        });
+        t.assertEqual('<u>0a</u><u>1b</u><u>2c</u>', div.html());
       },
 
       testText: function(t){