Question

I need to check whether information entered are 3 character long, first one should be 0-9 second A-Z and third 0-9 again.

I have written pattern as below:

var pattern = `'^[A-Z]+[0-9]+[A-Z]$'`;
var valid = str.match(pattern);

I got confused with usage of regex for selecting, matching and replacing.

• In this case, does[A-Z] check only one character or whole string ?
• Does + separate(split?) out characters?

Answer 1

1) + matches one or more. You want exactly one

2) declare your pattern as a REGEX literal, inside forward slashes

With these two points in mind, your pattern should be

/^[A-Z][0-9][A-Z]$/

Note also you can make the pattern slightly shorter by replacing [0-9] with the \d shortcut (matches any numerical character).

3) Optionally, add the case-insensitive i flag after the final trailing slash if you want to allow either case.

4) If you want to merely test a string matches a pattern, rather than retrieve a match from it, use test(), not match() – it’s more efficient.

var valid = pattern.test(str); //true or false