How can you define a default value for a property in an LWC?

Defining a default value for a property in a Lightning Web Component (LWC) is commonly done by initializing the property in the constructor. This approach allows you to set default values directly within your component’s JavaScript class, ensuring that whenever an instance of the component is created, the properties are initialized to known values.

This initialization happens before the component is rendered, which means that the property is available for use in the template from the moment the component is initialized. This is particularly useful for properties that will drive initial component rendering or default behavior. For example, if you have a boolean property that manages whether a section is shown or hidden, you can set its default state in the constructor.

Using the @api decorator merely marks a property as public, making it accessible to the parent component, but it does not provide a mechanism to set default values. Defining properties in a separate file does not conform to LWC structure as properties need to be defined within the specific component’s class. Setting properties after the component is rendered would not provide default values at initialization time, meaning they could lead to unexpected behaviors if not managed correctly.

Thus, initializing the property in the constructor is the most reliable and straightforward method to define default values in LWC