Multiple left-hand assignment with JavaScript

var var1 = 1,
    var2 = 1,
    var3 = 1;

This is equivalent to this:

var var1 = var2 = var3 = 1;

I’m fairly certain this is the order the variables are defined: var3, var2, var1, which would be equivalent to this:

var var3 = 1, var2 = var3, var1 = var2;

Is there any way to confirm this in JavaScript? Using some profiler possibly?