js trim函数 js去空格函数与正则

//供使用者调用
function trim(s){
return trimright(trimleft(s));
}
//去掉左边的空白
function trimleft(s){
if(s == null) {
return "";
}
var whitespace = new string(" \t\n\r");
var str = new string(s);
if (whitespace.indexof(str.charat(0)) != -1) {
var j=0, i = str.length;
while (j < i && whitespace.indexof(str.charat(j)) != -1){
j++;
}
str = str.substring(j, i);
}
return str;
}
//去掉右边的空白
function trimright(s){
if(s == null) return "";
var whitespace = new string(" \t\n\r");
var str = new string(s);
if (whitespace.indexof(str.charat(str.length-1)) != -1){
var i = str.length - 1;
while (i >= 0 && whitespace.indexof(str.charat(i)) != -1){
i--;
} // www.jiaochengji.com
str = str.substring(0, i+1);
}
return str;
}

<script language="javascript">
<!--
string.prototype.trim = function()
{
return this.replace(/(^\s*)|(\s*$)/g, "");
}
string.prototype.ltrim = function()
{
return this.replace(/(^\s*)/g, "");
}
string.prototype.rtrim = function()
{
return this.replace(/(\s*$)/g, "");
}
//-->
</script>
<input type="text" value="    前后都是空格   " id="space">
<input type="button" value="去前后空格" onclick="javascript:document.getelementbyid('space').value=document.getelementbyid('space').value.trim();document.getelementbyid('space').select();">
<input type="button" value="去前空格" onclick="javascript:document.getelementbyid('space').value=document.getelementbyid('space').value.ltrim();document.getelementbyid('space').select();">
<input type="button" value="去后空格" onclick="javascript:document.getelementbyid('space').value=document.getelementbyid('space').value.rtrim();document.getelementbyid('space').select();">
<input type="button" value="还原" onclick="javascript:document.getelementbyid('space').value='    前后都是空格     ';">