Will new Date().toJSON() always be unique in Javascript?

Question

The PouchDB Manual suggests using Date().toJSON() to generate a new id for each document. Do all javascript runtimes guarantee that Date().toJSON() will always be unique?

Answer 1

The dates only have microsecond precision, so there's no guarantee they will be unique.

The snippet below will give you a number of duplicates in all but the slowest runtime environments:

for (let i = 0; i < 10; i++) {
  console.log(new Date().toJSON())
}