a few changes to increase jQuery compatibility.

src/zepto.js

@@ -539,15 +539,15 @@ var Zepto = (function() {
     prev: function(selector){ return $(this.pluck('previousElementSibling')).filter(selector || '*') },
     next: function(selector){ return $(this.pluck('nextElementSibling')).filter(selector || '*') },
     html: function(html){
-      return html === undefined ?
+      return arguments.length === 0 ?
         (this.length > 0 ? this[0].innerHTML : null) :
         this.each(function(idx){
           var originHtml = this.innerHTML
           $(this).empty().append( funcArg(this, html, idx, originHtml) )
         })
     },
     text: function(text){
-      return text === undefined ?
+      return arguments.length === 0 ?
         (this.length > 0 ? this[0].textContent : null) :
         this.each(function(){ this.textContent = text })
     },
@@ -579,7 +579,7 @@ var Zepto = (function() {
       return data !== null ? deserializeValue(data) : undefined
     },
     val: function(value){
-      return (value === undefined) ?
+      return arguments.length === 0 ?
         (this[0] && (this[0].multiple ?
            $(this[0]).find('option').filter(function(o){ return this.selected }).pluck('value') :
            this[0].value)