Can I use a javascript regex to count the number of whitespace characters before the first text character in the string? I only care if there are 0, 1, and 2+.
My current working solution is to have three regexes and just use match to determine the 0,1, or 2+ category(separate pattern for each), but Im looking for a more elegant solution.
Is it even possible to count patterns with regex? I could use a non-greedy grouping and count the length I guess....
" a".match(/^\s{0,2}/)[0].length
This regex matches between 0 and 2 whitespace characters at the beginning of a string.
theString.match(/^\s+/)[0].length -- the OP means, I think 2+ to mean two or more, although it was strangely worded.
str.replace(/^\s*(.*?)\s*$/,"$1")\s* by the way. Good answer!!I'm not sure I'd use a regex in real life for this job, but you can match them in a capture and the see their length:
function countLeadingSpaces(str) {
return(str.match(/^(\s*)/)[1].length;
}
A non regex way designed for speed (pretty much anything is fast compared to a regex):
function countLeadingSpaces2(str) {
for (var i = 0; i < str.length; i++) {
if (str[i] != " " && str[i] != "\t") {
return(i);
}
}
return(str.length);
}
\s* and get rid of the "matches" check altogether?
/^(\s*)[^ \t]/ of an empty string returns null which means you can't directly dereference [1].length on a match using it without some sort of check. I'm not suggesting my method is the most compact, but I was trying to be safe for all edge cases.[ \t] bit. Since the regexes are greedy anyway, you can just use ^(\s*) on its own.You could find the index of the first non-space character in the string, which is the same as the number of leading white space characters.
t.search(/\S/);
If you insist you can limit the return to 0, 1 or 2 with Math.min(t.search(/\S/), 2);
If there are no non-space characters the return will be -1....
Why not just use a capture group and check the length:
<html>
<head>
</head>
<body>
<script language="javascript">
var myStr = " hello";
var myRe = /^(\s*)(.*)$/;
var match = myRe.exec(myStr);
alert(match[1].length); // gives 2
alert(match[2]); // gives "hello"
</script>
</body>
</html
This can be followed by code that acts on your three cases, a length of 0, 1 or otherwise, and acts on the rest of the string.
You should treat regexes as the tool they are, not as an entire toolbox.