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sioesi
Asked: 2020-03-29 06:24:20 +0800 CST 2020-03-29 06:24:20 +0800 CST

Validate 2 regular expressions in one

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I have the following regular expression

/^(([^<>()\[\]\.,;:\s@\"]+(\.[^<>()\[\]\.,;:\s@\"]+)*)|(\".+\"))@(([^<>()[\]\.,;:\s@\"]+\.)+[^<>()[\]\.,;:\s@\"]{2,})$/i

To validate emails, I must also validate that the email does not contain the word "does not have" and the expression is /^((?!notiene).)*$, however I cannot mix the two.

javascript

1 Answers

  1. Best Answer

    The problem . The negative lookahead you are using starts from the beginning of the text, and consumes each one of the characters as long as they are not followed bynotiene

    /^((?!notiene).)*$/

    This means that when you try to validate the mail, it will already be found at the end of the text. That is, the .*one of that pattern has already consumed all the characters, without allowing more to be validated.

    The solution . On the other hand, if it is validated from the beginning of the text, but no character is consumed, then more than one subpattern can be validated:

    /^(?!.*notiene)expresión2$/i

    An inspection attempts to match the subpattern, and after matching, the cursor continues from the same position it was in before the inspection was attempted. It can be thought of as a construct that only returns true/false, but the rest of the regex can continue as if nothing had happened ( if it returned true, of course ).

    With ^(?!.*notiene)we make sure that the entire line is traversed. If .*notieneit doesn't match, being a negative check then it's like it returns " true ", but we're still at the beginning of the text (no characters were consumed), and we can check any other patterns from there.


    Full Regex: (using the answer from Validate an email in JavaScript )

    /^(?!.*notiene)(?:[^<>()[\].,;:\s@"]+(\.[^<>()[\].,;:\s@"]+)*|"[^\n"]+")@(?:[^<>()[\].,;:\s@"]+\.)+[^<>()[\]\.,;:\s@"]{2,63}$/i


    demonstration:

    document.getElementById('email').addEventListener('input', function(evt) {
    campo = evt.target;
    valido = document.getElementById('emailOK');
        
    emailRegex = /^(?!.*notiene)(?:[^<>()[\].,;:\s@"]+(\.[^<>()[\].,;:\s@"]+)*|"[^\n"]+")@(?:[^<>()[\].,;:\s@"]+\.)+[^<>()[\]\.,;:\s@"]{2,63}$/i;
    //Se muestra un texto a modo de ejemplo
    if (emailRegex.test(campo.value)) {
      valido.innerText = "válido";
    } else {
      valido.innerText = "incorrecto";
    }
});
    Email que no tenga "notiene":
<input id="email">
<span id="emailOK"></span>


    overall case

    For any case where we have 2 regular expressions anchored at the beginning of the text (yes, they have to match from the beginning), let them be ^re1and ^re2, the way to check both is:

    /^(?=re1)re2/

    Or, as in your case, that the first does not match, but the second does:

    /^(?!re1)re2/


    For example, joining 3 expressions: that has a capital letter, that does not end in "1234" and that has between 8 and 200 characters .

    /^(?=.*[A-ZÁÉÍÓÚÜÑ])(?!.*1234$).{8,200}$/
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