foo.js

function createFoo(foo) {
  // 3rd party lib
  return newFooId
}

function deleteFoo(fooId) {
  // 3rd party lib
}

function doTheThing() {
  var foo = {
    name: "Thing",
    onClick: function() {
      deleteFoo(fooId)
    }
  }
  
  var fooId = createFoo(foo)
}