function thisIsBad ({
    someKey: renamedSomeKey,
    someOtherKey: renamedSomeOtherKey = 'otherDefaultValue',
    meta: { innerMetaKey = 'someInnerMetaKeyValue', otherInnerMetaKey, ...remainingMeta }
  } = {
    someKey: 'defaultValue',
    someOtherKey: SOME_CONSTANT,
    meta: {}
  }) {
    // ...
    return { someKey: renamedSomeKey }
  }

My favourite messed up part of the syntax is the way the `:` character is used to describe either the default value of a property or a way of renaming the name of a property internally (depending on whether it is to the left or right of an `=`). And also, the way you can destructure the inside of an object, and automatically lose the original value. For example `meta` is not accessible within the function defined above.

This is syntax which can simplify your code if you apply it carefully, but will ruin your code if you over-use it.