if (obj != null && obj.constructor === Object && Object.keys(obj).length === 0) {
  // do something
}

The constructor === Object check matters — without it, things like '', 0, 42 and [] also pass the “no keys” test and get treated as empty objects. Object.keys beats Object.entries here too: no point allocating all those [key, value] pairs just to count them.

As a function:

export const isObjectEmpty = (obj: unknown): boolean => {
  return (
    obj != null &&
    obj.constructor === Object &&
    Object.keys(obj).length === 0
  )
}

// isObjectEmpty({}) true
// isObjectEmpty({a: 1}) false
// isObjectEmpty([]) false
// isObjectEmpty('') false

You can also invert that function to check if an object has values.

export const isObjectFull = (obj) => !isObjectEmpty(obj)

Not sure about the naming of this one, but you get the idea