The useMap property on the HTMLImageElement interface reflects the value of the HTML usemap attribute, which is a string providing the name of the client-side image map to apply to the image.

A string providing the page-local URL (that is, a URL that begins with the hash or pound symbol, "#") of the <map> element which defines the image map to apply to the image.

You can learn more about client-side image maps in our learning article Add a hitmap on top of an image.

The string value of useMap must be a valid anchor for a <map> element. In other words, this string should be the value of the appropriate <map>'s name attribute with a pound or hash symbol prepended to it.

Consider a <map> that looks like this:

<map name="mainmenu-map">
  <area
    shape="circle"
    coords="25, 25, 75"
    href="/index.html"
    alt="Return to home page" />
  <area shape="rect" coords="25, 25, 100, 150" href="/index.html" alt="Shop" />
</map>

Given the image map named mainmenu-map, the image which uses it should look something like the following:

<img src="menubox.png" usemap="#mainmenu-map" />

For additional examples (including interactive ones), see the articles about the <map> and <area> elements, as well as the guide to using image maps.