2 个大写字母和 3 个数字的正则表达式

Question

I need to match words that contains exactly 2 uppercase letters and 3 numbers. Numbers and uppercase letters can be at any positions in the word.

HelLo1aa2s3d: true

WindowA1k2j3: true

AAAsjs21js1: false

ASaaak12: false

My regex attempt, but only matches exactly 2 uppercase letters:

([a-z]*[A-Z]{1}[a-z]*){2}

Answer 1

You can use regex lookaheads :

/^(?=(?:.*[A-Z].*){2})(?!(?:.*[A-Z].*){3,})(?=(?:.*\d.*){3})(?!(?:.*\d.*){4,}).*$/gm

Explanation:

^                     // assert position at beginning of line
(?=(?:.*[A-Z].*){2})  // positive lookahead to match exactly 2 uppercase letters
(?!(?:.*[A-Z].*){3,}) // negative lookahead to not match if 3 or more uppercase letters
(?=(?:.*\d.*){3})     // positive lookahead to match exactly 3 digits
(?!(?:.*\d.*){4,})    // negative lookahead to not match if 4 or more digits
.*                    // select all of non-newline characters if match
$                     // end of line
/gm                   // flags: "g" - global; "m" - multiline

Regex101

Answer 2

The solution using String.match function:

function checkWord(word) {
    var numbers = word.match(/\d/g), letters = word.match(/[A-Z]/g);

    return (numbers.length === 3 && letters.length === 2) || false;
}

console.log(checkWord("HelLo1aa2s3d"));  // true
console.log(checkWord("WindowA1k2j3"));  // true
console.log(checkWord("AAAsjs21js1"));   // false
console.log(checkWord("ASaaak12"));      // false

Answer 3

I think, you need just one lookahead.

^(?=(?:\D*\d){3}\D*$)(?:[^A-Z]*[A-Z]){2}[^A-Z]*$

• \\d is a short for digit. \\D is the negation of \\d and matches a non-digit
• (?= opens a positive lookahead . (?: opens a non capturing group .
• At ^ start (?=(?:\\D*\\d){3}\\D*$) looks ahead for exactly three digits until $ the end .
• If the condition succeeds (?:[^AZ]*[AZ]){2}[^AZ]* matches a string with exactly two upper alphas until $ end. [^ opens a negated character class .

Demo at regex101

If you want to allow only alphanumeric characters, replace [^AZ] with [az\\d] like in this demo .

Answer 4

Without lookahead, pure regex:

http://regexr.com/3ddva

Basically, just checks every case.