HTMLInputElement: valueAsNumber property

The valueAsNumber property of the HTMLInputElement interface represents the current value of the <input> element as a number or NaN if converting to a numeric value is not possible.

This property can also be set directly, for example to set a default numeric value based on some condition.

Value

A number that represents the value of the element or NaN if numeric conversion is impossible.

Examples

Retrieving a number value

In this example, the log displays the current value of the number input when changed.

HTML

We include an <input> of type number and an associated <label>, with a <pre> container for our output.

<label for="number">Pick a number between 1 and 10:</label>

<input name="number" id="number" min="1" max="10" type="number" />

<pre id="log"></pre>

JavaScript

The <pre> element's innerText is updated to the current value of the <input> every time a change event is fired.

const logElement = document.getElementById("log");
const inputElement = document.getElementById("number");

inputElement.addEventListener("change", () => {
  logElement.innerText = `Number: ${inputElement.valueAsNumber}`;
});

Results

If you delete the number in the widget, the result is NaN.

Retrieving a date value as a number

This example demonstrates the valueAsNumber property of an <input> with type datetime-local.

HTML

We include an <input> of type datetime-local:

<label for="date">Pick a date and time:</label>

<input name="date" id="date" type="datetime-local" />

<pre id="log"></pre>

JavaScript

When no date or time is selected, the empty string resolves to NaN. Each time a selection is made, a change event is fired, updating the <pre> content showing the HTMLInputElement.value of the form control compared to that value as a number.

const logElement = document.getElementById("log");
const inputElement = document.getElementById("date");

logElement.innerText = `Initial value: ${inputElement.valueAsNumber}`;

inputElement.addEventListener("change", () => {
  const d = new Date(inputElement.valueAsNumber);
  logElement.innerText = `${inputElement.value} resolves to ${inputElement.valueAsNumber}, \nwhich is ${d.toDateString()} at ${d.toTimeString()}`;
});

Results

Specifications

Browser compatibility

See also

• <input>
• HTMLInputElement.value
• HTMLInputElement.valueAsDate