去除所有空格:???
str?? =?? str.replace(/\s+/g,"");???????
去除两头空格:???
str?? =?? str.replace(/^\s+|\s+$/g,"");

去除左空格：

str=str.replace( /^\s*/, '');

去除右空格：

str=str.replace(/(\s*$)/g, "");

?

1. SCRIPT LANGUAGE="JavaScript"> ??
2. <!-- ??
3. //出处:网上搜集???
4. // Trim() , Ltrim() , RTrim()???
5. String.prototype.Trim = function() ??
6. { ??
7. return?this.replace(/(^\s*)|(\s*$)/g,?""); ??
8. } ??
9. String.prototype.LTrim = function() ??
10. { ??
11. return?this.replace(/(^\s*)/g,?""); ??
12. } ??
13. String.prototype.RTrim = function() ??
14. { ??
15. return?this.replace(/(\s*$)/g,?""); ??
16. } ??
17. //-->???
18. </SCRIPT> ??
19. <input type="text"?value="??? 前后都是空格???? "?id="space"> ??
20. <input type="button"?value="去前后空格"onclick="javascript:document.getElementById('space').value
21. =document.getElementById('space').value.Trim();document.getElementById('space').select();"> ??
22. 
    
23. <input type="button"?value="去前空格"onclick="javascript:document.getElementById('space').value=
24. document.getElementById('space').value.LTrim();document.getElementById('space').select();"> ??
25. 
    
26. <input type="button"?value="去后空格"onclick="javascript:document.getElementById('space').value=
27. document.getElementById('space').value.RTrim();document.getElementById('space').select();"