RegEx mismatch in node.js

Question

Consider the following regex:

^[^-\s][a-zA-Z\sàèìòùÀÈÌÒÙáéíóúýÁÉÍÓÚÝâêîôûÂÊÎÔÛãñõÃÑÕäëïöüÿÄËÏÖÜŸçÇßØøÅåÆæœ\d!@#$\+%&\'*]{1,20}$

I did try it on https://regexr.com/ using as test Collection '98 and matches.

I then did implement it in Node.js:

const myRegex = '^[^-\s][a-zA-Z\sàèìòùÀÈÌÒÙáéíóúýÁÉÍÓÚÝâêîôûÂÊÎÔÛãñõÃÑÕäëïöüÿÄËÏÖÜŸçÇßØøÅåÆæœ\d!@#$\+%&\'*]{1,20}$';

const name = 'Collection \'98';

if (!name.match(myRegex))
  console.log('NOK');
else
  console.log('OK');

However, it always prints NOK.

Why doesn't the validation work via app?

When a regex is passed as a string, backslashes are part of string escape sequences. If a string escape sequence is unknown, the backslash is omitted. Double them, or use regex literal notation. — Wiktor Stribiżew, May 12 '19 at 20:36

DjaouadNM · Answer 1 · 2019-05-12T20:42:46.117

1

Enclose your regex between slashes (/) instead of quotation marks " and it'll work:

const myRegex = /^[^-\s][a-zA-Z\sàèìòùÀÈÌÒÙáéíóúýÁÉÍÓÚÝâêîôûÂÊÎÔÛãñõÃÑÕäëïöüÿÄËÏÖÜŸçÇßØøÅåÆæœ\d!@#$\+%&\'*]{1,20}$/;

const name = 'Collection \'98';

if (!name.match(myRegex))
  console.log('NOK');
else
  console.log('OK');

edited May 12 '19 at 20:42

answered May 12 '19 at 20:33

DjaouadNM

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Emma · Answer 2 · 2019-05-12T20:41:16.103

I'm not sure about your codes, however it seems to me that your expression is correct and it works.

This snippets shows that it would return a match.

const regex = /[^-\s][a-zA-Z\sàèìòùÀÈÌÒÙáéíóúýÁÉÍÓÚÝâêîôûÂÊÎÔÛãñõÃÑÕäëïöüÿÄËÏÖÜŸçÇßØøÅåÆæœ\d!@#$\+%&\'*]{1,20}/gm;
const str = `Collection '98`;
let m;

while ((m = regex.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    // The result can be accessed through the `m`-variable.
    m.forEach((match, groupIndex) => {
        console.log(`Found match, group ${groupIndex}: ${match}`);
    });
}

You can test/modify your expressions in this link.

It appears that you might have forgotten to add your expression in between two forward slashes, which you can simply fix it using /expression/.

RegEx mismatch in node.js

2 Answers2