how to add javascript functionality to a variable

Hello I am trying to add a string in Javascript like .something(variable) on variable x which is defined as

   var x = white.reference(action)

if another variable returns false

so in hindsight if var y = false then .something(variable) will be added to var x to look something like

    x = white.reference(action).something(variable)

I am not sure how to approach this method and problem