How to Dynamically Set HTML5 Required Attribute Using Javascript

Setting HTML5 Required Attribute Dynamically Using Javascript

To dynamically set the required attribute in HTML5 using Javascript, follow the steps below:

Issue Overview

Attempting to set the required attribute using the recommended W3C syntax:

document.getElementById("edName").attributes["required"] = "";

doesn't trigger validation checks.

Correct Way to Set HTML5 Validation Boolean Attribute

The correct way to set an HTML5 validation boolean attribute is to use the element.required property.

For example:

document.getElementById("edName").required = true;

where edName is the ID of the input element.

Understanding the Attribute Value

In HTML5, boolean attributes can be defined either by:

• Leaving the attribute empty: required=""
• Using the attribute's canonical name: required="required"

However, when the required attribute is defined in the markup, the attribute's value is neither of these options:

edName.attributes.required = [object Attr]

This is because required is a reflected property, similar to id, name, and type.

Reflected Properties

Reflected properties are attributes that exist on the element object itself. Setting the value of a reflected property updates the corresponding attribute in the HTML.

Therefore, the following two methods are equivalent:

Using setter property:

element.required = true;

Using setAttribute:

element.setAttribute("required", "");

To clear a reflected property, use removeAttribute:

element.removeAttribute("required");

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