The mediaText property of the MediaList interface is a stringifier that returns a string representing the MediaList as text, and also allows you to set a new MediaList.

A string representing the media queries of a stylesheet. Each one is separated by a comma, for example screen and (min-width: 480px), print.

If you wish to set new media queries on the document, the string value must have the different queries separated by commas, e.g. screen, print. Note that the MediaList is a live list; updating the list via mediaText will immediately update the behavior of the document.

Also note that is you try to set mediaText to null, it will be treated as an empty string, i.e. the value will be set to "".

The following would log to the console a textual representation of the MediaList of the first stylesheet applied to the current document.

const stylesheets = document.styleSheets;
let stylesheet = stylesheets[0];
console.log(stylesheet.media.mediaText);