Currently, I am using /^[a-zA-Z.+-. ']+$/ regex to validate incoming strings.
When the incoming string is empty or only contains whitespace, I would like the code to throw an error.
How can I check for empty string using regex? I found some solutions but none are helpful.
You may use
/^(?! *$)[a-zA-Z.+ '-]+$/
Or - to match any whitespace
/^(?!\s*$)[a-zA-Z.+\s'-]+$/
The (?!\s*$) negative lookahead will fail the match if the string is empty or only contains whitespace.
Pattern details
^ - start of string(?!\s*$) - no empty string or whitespaces only in the string[a-zA-Z.+\s'-]+ - 1 or more letters, ., +, whitespace, ' or - chars$ - end of string.Note that actually, you may also use (?!\s+) lookahead here, since your pattern does not match an empty string due to the + quantifier at the end.
Check if the string is empty or not using the following regex:
/^ *$/
The regex above matches the start of the string (^), then any number of spaces (*), then the end of the string ($). If you would instead like to match ANY white space (tabs, etc.), you can use \s* instead of *, making the regex the following:
/^\s*$/
To check for empty or whitespace-only strings you can use this regex: /^\s*$/
Example:
function IsEmptyOrWhiteSpace(str) {
return (str.match(/^\s*$/) || []).length > 0;
}
var str1 = "";
var str2 = " ";
var str3 = "a b";
console.log(IsEmptyOrWhiteSpace(str1)); // true
console.log(IsEmptyOrWhiteSpace(str2)); // true
console.log(IsEmptyOrWhiteSpace(str3)); // false
if(string.match(/^\s?=*$/g).length > 0) // Not valid