The as property of the HTMLLinkElement interface returns a string representing the type of content to be preloaded by a link element.
The as property must have a value for link elements when rel="preload", or the resource will not be fetched. It may also be applied to link elements where rel="modulepreload", but if omitted, will default to script. The property should not be set for other types of link elements, such as rel="prefetch".
This property reflects the value of the as attribute of the <link> HTML element.