How to use the required attribute on a select dropdown?
Jul 11, 2025 am 02:20 AM
To ensure that the user must select an option from the drop-down menu in the HTML form, use the required property to perform required verification. 1. Add required attribute on the <select> tag, 2. Set the value of the first <option> to an empty string to trigger verification failure, 3. You can simulate the placeholder effect through disabled and selected, 4. For more flexible control, you can manually judge the selection of values ??in JavaScript. Correctly setting the null value option is the key to ensuring validation takes effect.
In HTML forms, if you want the user to have to select an option from the select dropdown menu instead of skipping this field, you can use the required property. It helps you implement basic form validation and ensures that users do not submit empty data.
Basic usage
Just add the required attribute to the <select></select> tag:
<select required> <option value="">Please select </option> <option value="1">Option One</option> <option value="2">Option 2</option> </select>
This way, the browser will block the form submission when the user does not select any valid options and prompt the user to fill in it.
Note: If the default
valueof the first option is an empty string (as in the example above), then when the user does not make a choice, the browser will consider this field empty, which triggers the required verification failure.
Similar effects with placeholder
Sometimes we want to display placeholder text like "Please select". Although <select> does not support the placeholder attribute, this effect can be simulated by setting the first <option> .
<select required> <option value="" disabled selected>Please select</option> <option value="apple">Apple</option> <option value="banana">Banana</option> </select>
disabled and selected are used here, so that "Please select" is only used as a prompt and cannot be selected again. By using required , users must choose other options.
Combined with JavaScript verification more flexible
Although native required is already very practical, in some complex scenarios, additional checks may be required in conjunction with JavaScript. for example:
- Determine whether the default prompt item is selected
- Manually trigger verification before AJAX submission
The sample code is as follows:
const select = document.querySelector('select');
if (!select.value || select.value === '') {
alert('Please select a valid option');
}This method is suitable when you need to handle multiple fields in a uniform manner, or if you don't want to rely on the browser's default prompt style.
Let's summarize
-
requiredcan be directly added to<select></select>to achieve required verification - The first option is best set to value. The empty string is used in conjunction with required.
- If you want to simulate the placeholder effect, you can add
disabled selected - When more complex control is needed, you can use JS to manually judge the value.
Basically all that, not complicated but easy to ignore: if the first option is not a null value, required may not work as expected . So setting the null value option is the key.
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