js中去除左右空格

由於javascript函數庫中沒有現成的去除字串空格的方法，於是寫了一個：

//去除左右空格

function trim(str)
        {
             var i,j;
             if(str == "")
             {
                return "";
             }
             for(i=0;i<str.length;i++)
             {
                if(str.charAt(i) != ' ')
                {
                    break;
                }
               
             }
             if( i >= str.length)
             {
                    return "";
             }
             for(j = str.length;j>0;j--)
             {
                if(str.charAt(j) !=' ')
                {
                    break;
                }
             }
             return str.substring(i,j);
        }

//去除左空格

function trim(str)
        {
             var i;
             if(str == "")
             {
                return "";
             }
             for(i=0;i<str.length;i++)
             {
                if(str.charAt(i) != ' ')
                {
                    break;
                }
               
             }
             if( i >= str.length)
             {
                    return "";
             } 
               return str.substring(i,str.length);
        }

//去除右空格

function trim(str)
        {
             var j;
             if(str == "")
             {
                return "";
             }
            for(j = str.length;j>0;j--)
             {
                if(str.charAt(j) !=' ')
                {
                    break;
                }
             }
             return str.substring(0,j);
        }