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UnexpectedCharacter
Asked: 2020-11-30 10:30:23 +0800 CST 2020-11-30 10:30:23 +0800 CST

How to validate that there is not a minimum of characters but there is a maximum?

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I am preparing a regular expression:

[a-zA-Z0-9._-]{20}

So far I'm dealing with the pre-"@" part of an email and I'm trying to do something like this:

[a-zA-Z0-9._-]{"*"-20}

Where "*" appears I try to put that it does not have a minimum size, but a maximum

How could I mount the expression?

The idea is to use it later to do this:
Email in multi-character format (letters, numbers, periods, or underscores, 20 maximum) followed by at sign, letters (20 maximum), period (1), and 2 or 3 letters .

javascript

1 Answers

  1. Best Answer

    The solution is to use {n,m}( cuantificador de rango), where nis the minimum number of possible occurrences and mthe maximum.

    Example:

    var re = /^[a-zA-Z0-9]{0,20}$/;

console.log(re.test('')); // 0 chars
console.log(re.test('1')); // 1 chars
console.log(re.test('12345678901234567890'));// 20 chars
console.log(re.test('123456789012345678901'));// 21 chars

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