HTMLFencedFrameElement: width property

The width property of the HTMLFencedFrameElement gets and sets the value of the corresponding <fencedframe> width attribute, which specifies the width of the element.

The size of the embedded content may be set by internal contentWidth and contentHeight properties of the <fencedframe>'s config object. In such cases, changing the width or height of the <fencedframe> will change the size of the embedded container on the page, but the document inside the container will be visually scaled to fit. The reported width and height of the embedded document (i.e. Window.innerWidth and Window.innerHeight) will be unchanged.

const frame = document.createElement("fencedframe");
frame.width = "480";