好像javascript中没有trim函数，应该用什么代替呢？

[xgy_p]

我要去掉某个字符串头尾的空格，应该怎样做呢？难道要一个个字符地charAt，然后再判断它是不是空格？另外一个延伸出来的问题是，我要知道某个字符串是否全部由空格造成的，我应该怎样做？

[fason]

<script language="JavaScript">
String.prototype.trim = function () {
return this.replace(/^\s*|\s*$/g,'');
};
alert(" hehe ".trim());
</script>

[ghlfllz]

/*************************************************************
名称：trim
功能：去掉左右两边的空格
参数：sourcestr，源字符串；
返回：空格去完的字符串
*************************************************************/
function trim(sourcestr) {
sourcestr=sourcestr.replace(/^\s*/,"");
return sourcestr.replace(/\s*$/,"");
}

[joe820302]

<SCRIPT LANGUAGE="Javascript">
/*
==================================================================
LTrim(string) : Returns a copy of a string without leading spaces.
==================================================================
*/
function LTrim(str)
/*
PURPOSE: Remove leading blanks from our string.
IN: str - the string we want to LTrim
*/
{
var whitespace = new String(" \t\n\r");

var s = new String(str);

if (whitespace.indexOf(s.charAt(0)) != -1) {
// We have a string with leading blank(s)...

var j=0, i = s.length;

// Iterate from the far left of string until we
// don't have any more whitespace...
while (j < i && whitespace.indexOf(s.charAt(j)) != -1)
j++;

// Get the substring from the first non-whitespace
// character to the end of the string...
s = s.substring(j, i);
}
return s;
}

/*
==================================================================
RTrim(string) : Returns a copy of a string without trailing spaces.
==================================================================
*/
function RTrim(str)
/*
PURPOSE: Remove trailing blanks from our string.
IN: str - the string we want to RTrim

*/
{
// We don't want to trip JUST spaces, but also tabs,
// line feeds, etc. Add anything else you want to
// "trim" here in Whitespace
var whitespace = new String(" \t\n\r");

var s = new String(str);

if (whitespace.indexOf(s.charAt(s.length-1)) != -1) {
// We have a string with trailing blank(s)...

var i = s.length - 1; // Get length of string

// Iterate from the far right of string until we
// don't have any more whitespace...
while (i >= 0 && whitespace.indexOf(s.charAt(i)) != -1)
i--;


// Get the substring from the front of the string to
// where the last non-whitespace character is...
s = s.substring(0, i+1);
}

return s;
}

/*
=============================================================
Trim(string) : Returns a copy of a string without leading or trailing spaces
=============================================================
*/
function Trim(str)
/*
PURPOSE: Remove trailing and leading blanks from our string.
IN: str - the string we want to Trim

RETVAL: A Trimmed string!
*/
{
return RTrim(LTrim(str));
}

alert(Trim(" abc "));
alert(Trim(" ")=="");
</SCRIPT>

[心云意水]

当一个字符串trim后，长度为0表示该字符串全部由空格组成
<script language="JavaScript">
String.prototype.trim = function () {
return this.replace(/^\s*|\s*$/g,'');
};
alert(" hehe ".trim());
if(" ".trim().length==0)
alert("全部是空格！")
</script>

[cuixiping]

String.prototype.Trim = function(){return this.replace(/^\s+|\s+$/g,"");}

alert(" ".Trim()=="")

[kingchang2000]

呵呵，都是正则表达式，你在添上一个全角空格吧，反正都要被trim掉的