In WebGL, is it possible to write to the fragment's depth value or control the fragment's depth value in some other way?

As far as I could find, gl\_FragDepth is not present in webgl 1.x, but I am wondering if there is any other way (extensions, browser specific support, etc) to do it.

What I want to archive is to have a ray traced object play along with other elements drawn using the usual model, view, projection.