Hello,
How do I check if a field (textbox) is empty or filled only with white spaces (spaces/enters/tabs etc.), using javascript RegExp?
+5
A:
if (myField.value.match(/\S/)) {
// field is not empty
}
Explanation, since other people seem to have some crazy different ideas:
\s will match a space, tab or new line.
\S will match anything but a space, tab or new line.
If your string has a single character which is not a space, tab or new line, then it's not empty.
Therefore you just need to search for one character: \S
nickf
2008-11-20 06:41:46
test() is on the RegExp object: "/\S/.test(myField.value)"
Tomalak
2008-11-20 07:58:44
ya, i always get those two mixed up.
nickf
2008-11-20 08:06:37
I like the simplicity of the approach. But I don't think negated negative logic ("if not value contains non-space chars") contributes a lot to code comprehensibility.
Tomalak
2008-11-20 08:29:50
+1
A:
See answers to a similar question: recommendation for javascript form validation library.
gimel
2008-11-20 06:45:11
+3
A:
/^\s*$/.test(string)
Could be used like so:
var empty_string = /^\s*$/; //create RegExp object for re-use
if (empty_string.test(myFormField.value))
{
alert("Please be a bit more elaborate!");
}
Tomalak
2008-11-20 07:24:50
A:
Geo
2008-11-20 07:30:32
The latter will fail for the empty string. I am relatively sure the question author wants to include that as well. And why do you use "\S"? It will match *anything but* whitespace, so it's wrong here.
Tomalak
2008-11-20 07:40:10
I know . This will work in 2 ways : you test the /^\s+/ for matching , or you test the /^\S+/ for non-matching .
Geo
2008-11-20 07:49:09
Nevertheless this is non-obvious, you should make the distinction clearer in your answer.
Tomalak
2008-11-20 07:55:33
/^\S+$/ will give you a false positive on the input: "This is not empty". /^\s+$/ will give you a false negative on the input: "". If you find any ONE character which is not \s (ie: \S), then it's not empty. it's very simple!
nickf
2008-11-20 08:09:43