正则表达式：如何匹配非ASCII字符串的所有大写字符

Question

I have strings like Japan Company , Chinese Company , and this regex /([AZ])/g to get all uppercase characters then joining the result to make an emission of them. But when the input string is not in English letters then the regex does not work.

let string = "Japan Company";
console.log(string.match(/[A-Z]/g).join('')); // JC

But when I have a string like日本の会社

let string = "日本の会社";
console.log(string.match(/[A-Z]/g).join(''));

This throws an exception as the result of the string.match(/[AZ]/g) is null .

As I am trying to make elision to these strings and hieroglyphs do not have uppercases, the regex should match only first characters of each word where words are separated by spaces.

What generic regex should I use for this?

Something like POSIX's [:upper:] but this does not work for JavaScript regex engine.

Answer 1

You can use

(string.match(/(?<!\S)\S/g) || [string]).join('')

See the JavaScript demo:

 const strings = ["Japan Company", "japan company", "日本の会社"]; for (const string of strings) { console.log(string, '=>', (string.match(/(?<!\S)\S/g) || [string]).join('').toUpperCase()) }

The (?<!\S)\S regex matches a non-whitespace char at the start of string or after a whitespace char.

A Safari, non-lookbehind, pattern:

 var strings = ["Japan Company", "japan company", "日本の会社"]; for (var i=0; i<strings.length; i++) { var m = strings[i].match(/(?:^|\s)(\S)/g) if (m === null) { console.log(strings[i], '=> ', strings[i]) } else { console.log(strings[i], '=>', m.join('').replace(/\s+/g, '').toUpperCase()) } }

Answer 2

Based on your comments, I think this should do what you want.

function getUppercaseLetters(string) {
    // Find uppercase letters in the string
    let matches = string.match(/[A-Z]/g);
    // If there are no uppercase letters, get the first letter of each word
    if (!matches) matches = string.split(" ").map(word => word[0]);
    // If there are still no matches, return an empty string. This should prevent against any edge cases.
    if (!matches) return "";
    // Join the array elements and make it uppercase.
    return matches.join("").toUpperCase();
}