How to stop regex from picking up character matches when Ctrl, Shift, etc. are pressed?-CodePudding

I was tasked with making a code that picks up when a key is pressed and counts the number of characters typed. I decided to use var regex=/[a-zA-Z0-9]/;, but to my surprise, when I pressed Enter, Shift, Ctrl, or Alt, it would register all of them.

Here is the snippet of code that matters:

window.onload = init;

function init() {
    window.onkeyup = incrementKey;
}

function incrementKey() {
    console.log(event.key)

    var regex=/[a-zA-Z0-9]/;

    if (event.key.match(regex)) {
        console.log(event.key)
    }
}

This way I’ll see the character show up twice if picked up by regex, and once if not. And I have already tried nearly everything on the W3Schools documentation on RegExp.

Things that I tried: [A-Za-z0-9], [^\n] (also tried with \0, \n, \f, \r, \t, \v), [\w], [] (obviously, at least, here, it doesn’t register any keys).

I was wondering how I can exclude the characters that don’t change the context of the text, other than manually typing every single character on its own.

CodePudding user response：

If you want to use a regex to filter out the a-zA-Z0-9 characters then your original almost correct what your looking for is ^[a-zA-Z0-9]$ this regex will only match one character; anything between ^ and $ in a regex means that the pattern must start at the beginning of a string and end at the end of a string. Your original answer failed because [a-zA-Z0-9] searches the string for all one character long alphanumerical substrings, obviously the string "Enter" still has alphanumerical characters therefore your regex.match will result in a match.

Alse you could consider using regex.test(str) as it returns a boolean, you can read more about it over at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/test