用脚本(JavaScript)去掉字符串的前后空格

function Trim(str)
{

var i = 0;
var len = str.length;
if ( str == "" ) return( str );
j = len -1;
flagbegin = true;
flagend = true;
while ( flagbegin == true && i< len)
{
if ( str.charAt(i) == " " )
{
i=i+1;
flagbegin=true;
}
else
{
flagbegin=false;
}
}

while (flagend== true && j>=0)
{
if (str.charAt(j)==" ")
{
j=j-1;
flagend=true;
}
else
{
flagend=false;
}
}

if ( i > j ) return ("")

trimstr = str.substring(i,j+1);
return trimstr;
}