ValidityState: patternMismatch property

The read-only patternMismatch property of a ValidityState object indicates if the value of an <input>, after having been edited by the user, does not conform to the constraints set by the element's pattern attribute.

The patternMismatch property will be true if and only if the following conditions are all true:

Examples

Given the following:

html

<p>
  <label
    >Enter your phone number in the format (123)456-7890 (<input
      name="tel1"
      type="tel"
      pattern="[0-9]{3}"
      placeholder="###"
      aria-label="3-digit area code"
      size="2" />)-
    <input
      name="tel2"
      type="tel"
      pattern="[0-9]{3}"
      placeholder="###"
      aria-label="3-digit prefix"
      size="2" />
    -
    <input
      name="tel3"
      type="tel"
      pattern="[0-9]{4}"
      placeholder="####"
      aria-label="4-digit number"
      size="3" />
  </label>
</p>

Here we have 3 sections for a North American phone number with an implicit label encompassing all three components of the phone number, expecting 3-digits, 3-digits and 4-digits respectively, as defined by the pattern attribute set on each.

If the values are too long or too short, or contain characters that aren't digits, patternMismatch will be true. When true, the element matches the :invalid CSS pseudo-classes.

css

input:invalid {
  border: red solid 3px;
}

Note, in this case, we get a patternMismatch not a validityState.tooLong or validityState.tooShort if the values are too long or too short because it is the pattern that is dictating the length of the value. Had we used minlength and maxlength attributes instead, we may have seen validityState.tooLong or validityState.tooShort being true.

Note: The email input type requires, at minimum, a match of x@y and the url type requires, at minimum, a match to x:, with no pattern attribute present. When invalid, the validityState.typeMismatch will be true, if there is no pattern attribute (or if the pattern attribute is not valid for that input type).

Specifications

Specification
HTML Standard
# dom-validitystate-patternmismatch

Browser compatibility

BCD tables only load in the browser

See also