How do you control blendShape value in javascript?

I've imported a mesh from maya with blendshapes and when i click and drag the name (pageTest) i can see the animation. How do i control this value with javascript? For example dragging on the mesh with mouse0 down would increment the blendshape value. I've been searching for blendshape related scripting on this site and can't seem to find anything.

PS I'm a total noob at unity. Thanks!