How get opacity param in rgba using javascript

Question

I wanna know how i can get the opacity param using javascript / jQuery.

For exemple : rgba(255,255,255,0.5)

I need to get 0.5

Thanks

Answer 1

In case if "rgba(255,255,255,0.5)" is string:

var rgba="rgba(255,255,255,0.5)";
var alpha=rgba.replace(/^.*,(.+)\)/,'$1')