Get the data from the server using the regular expression of JS to space _javascript tips

I've been having a stupid question this morning, and I haven't found it.
If $str= "";
$STR = "$str-$sno";

So down, $str front will have a space, JS get this value, you must remove the space

Go to the Space function Rstr=rstr.replace (/(^\s*) | ( \s*$)/g, "");

Other:

Go to left space replace (/(^\s*)/g, "");

Go to right space replace (/(\s*$)/g, "");

In addition, if you do a step-by-step check of the program flow, stop at if, you must output two values in the IF, compare, or add a # to see if there are spaces

To sum up

1, where the string is connected to the place, may produce spaces, and then split the time, it appeared with the original do not want to wait, therefore, must be removed before and after the space

2, especially in obtaining data from the server, JS must pay attention to the occurrence of the space may