Show Waveform Using Extend Script

I'm looking for a way to code a script that displays the waveforms for all layers in a comp that have an audio component. Essentially the same as pressing 'L' shortcut twice, except I'm looking to run a script that does this for every layer in every comp in the project. 

Basically, I'm looking to enable the waveform and also show the audio level keyframes, and the opacity keyframes all at once, for every layer in every comp. 

How can I use extend script to get (to start with) just the waveform showing in the timeline?

I tried: 

var item = app.property.activeItem;
item.property("Opacity").enabled = true;