js 去除左右首尾空格

ie6不支持jquery的trim()方法，于是找来这个代码备用 

Js代码  
>>> "sss".replace(/^\s+|\s+$/g, "")   
"sss"  
  
>>> " sss".replace(/^\s+|\s+$/g, "")   
"sss"  
  
>>> " sss ".replace(/^\s+|\s+$/g, "")   
"sss"  
  
>>> " s s s ".replace(/^\s+|\s+$/g, "")   
"s s s"