ValidityState: rangeUnderflow property - Web APIs | MDN (original) (raw)

Baseline

Widely available

The read-only rangeUnderflow property of the ValidityState interface indicates if the value of an , after having been edited by the user, does not conform to the constraints set by the element's min attribute.

If the field is numeric in nature, including the date, month, week, time, datetime-local, number and range types and a min value is set, if the value doesn't conform to the constraints set by the min value, the rangeUnderflow property will be true.

Value

A boolean that is true if the ValidityState does not conform to the constraints.

Examples

Input with numeric underflow

The following example checks the validity of a numeric input element. A constraint has been added using the min attribute which sets a minimum value of 18 for the input. If the user enters a number lower than 18, the element fails constraint validation, and the styles matching :invalid and :out-of-range CSS pseudo-classes

/* or :invalid */
input:out-of-range {
  outline: red solid 3px;
}

body {
  margin: 0.5rem;
}
pre {
  padding: 1rem;
  height: 2rem;
  background-color: lightgrey;
  outline: 1px solid grey;
}

<pre id="log">Validation logged here...</pre>
<input type="number" id="age" min="18" />

const userInput = document.getElementById("age");
const logElement = document.getElementById("log");

function log(text) {
  logElement.innerText = text;
}

userInput.addEventListener("input", () => {
  userInput.reportValidity();
  if (userInput.validity.rangeUnderflow) {
    log("Number is too low!");
  } else {
    log("Valid…");
  }
});

Specifications

Browser compatibility

See also