Only allow whitespace after comma and restrict special characters in text field using regex

user_992731 0
Viewed 608

I am trying to restrict a user from being able to enter whitespace or hit the spacebar after characters (unless they enter a comma) as well as restrict all special characters except numbers and letters.

The desired output would be something like: "ab, c" or "abc, def, g, h..." The user would only be allowed to have whitespace or hit the spacebar after a comma. A comma is the only special character permitted.

What I have so far but it's only allowing for 1 comma:

function checkKey() {
    var clean = this.value.replace(/[^0-9,]/g, "")
                           .replace(/(,.*?),(.*,)?/, "$1");
    // don't move cursor to end if no change
    if (clean !== this.value) this.value = clean;
}

// demo
document.querySelector('input').oninput = checkKey;
javascript regex
2 Answers

In your code .replace(/[^0-9,]/g, "") , you are removing all chars except digits and a comma, not allowing chars a-z anymore.

You can first remove all characters except [^a-zA-Z0-9, ]+, and then in browsers that support a lookbehind, you can allow a space when it is not directly preceded by a comma.

function checkKey() {
  const clean = this.value
    .replace(/[^a-zA-Z0-9, ]+/g, "")
    .replace(/(?<!,) /g, "");
  if (clean !== this.value) this.value = clean;
}

document.querySelector('input').oninput = checkKey;
<form>
  <input type="text">
</form>

user_54249880

To remove all whitespaces after a non-comma char, you can use this solution with no lookbehind:

.replace(/(^|[^,])\s+/g, "$1")

See this regex demo. Details:

  • (^|[^,]) - Capturing group 1 ($1 refers to this group value): start of string (^) or (|) any non-comma char ([^,])
  • \s+ - one or more whitespaces.

In your code:

function checkKey() {
    var clean = this.value.replace(/[^\d,]/g, "").replace(/(^|[^,])\s+/g, "$1");
    if (clean !== this.value) {
        this.value = clean;
    }
}
user_38329700
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