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Accepted
Paul
Asked: 2022-02-07 14:20:57 +0800 CST 2022-02-07 14:20:57 +0800 CST

How to know if a string is alphanumeric with Javascript?

  • 772

For example, I have the string 11aa32bbb5and I want to extract only the characters aa, bbbor the numbers11, 32, 5

How do I confirm that a letter or string is alphanumeric or not?

This is the implementation I have.

const checkChar = (ch) => {
    if (ch.charCodeAt(0) >= 97 && ch.charCodeAt(0) <= 122) {
        return true;
    };
    return false;
};

Thank you!

javascript

1 Answers

  1. Best Answer

    You can use a regular expression, as follows

    const filterAlpha = (str) => {
  if (typeof str !== "string") return false;
  return str.replace(/[A-Z]|[a-z]|[0-9]/g, "") === "";
}

console.log(filterAlpha("aabsbfsf"));
console.log(filterAlpha("xfdsdt32652aFDFGñ34532524"));
console.log(filterAlpha("adfasdgfesdgrdfñ25325tADDSG"));
console.log(filterAlpha("11aa32bbb5"));

    We replace both from A to Z and all the numbers of the string, so that if it is empty, it will logically be alphanumeric

    We combine 3 regular expressions:

    [A-Z]
[a-z]
[0-0]

    So we count from 0 to 9 for each number in the string, in addition to the letters A to Z in upper and lower case, we will use the /g operator to indicate that we are going to replace all existing matches, if we wanted to extract only the first matches would be as follows

    /[a-z-0-9]/i

    So the /i operator indicates ignore case , that is, it is not case sensitive.

    To extract the matches we can use.match

    console.log("243adfsdf25edh".match(/[A-Z]|[a-z]|[0-9]/g));
console.log("ñ".match(/[A-Z]|[a-z]|[0-9]/g));
console.log("ñ1abc".match(/[A-Z]|[a-z]|[0-9]/g));

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