JavaScript coding style for initializing variables
As you are not using ; consistently I would say that your init style is dangerous as it will block automatic colon insertion.

For example the following lines will throw a syntax error SyntaxError: Unexpected token '{'

 var a = foo{ 
    // init stuff
 }


Or syntax error Missing initializer in destructuring declaration

 var a = 0,{
    // init stuff
 }


In a sea of code this type of typo is easily overlooked. Though it is a syntax error so will not lay in wait (in most normal situations)

When you allow the ; to be inserted by moving the { to a new line it is safer.

 var a = foo
 { 
    // init stuff
 }


however the concern is that you are doing more than simple assignment within the block which could lead to situation such as

 var a = {}
 {
     let a.bar = foo  // was meant to be a.bar = foo
 }


The let is a typo but will not get caught until the code is run.

If you do continue to use this style I would recommend you use semicolons and be very strict in regards to the extent of the setup code within the block.

Personally I think its ugly.