You can log all property accesses on an object, e.g. for testing purposes. For example, see https://searchfox.org/mozilla-central/rev/da499aac682d0bbda5829327b

You can log all property accesses on an object, e.g. for testing purposes. For example, see https://searchfox.org/mozilla-central/rev/da499aac682d0bbda5829327b60a865cbc491611/testing/web-platform/tests/fetch/api/headers/headers-record.html#15-25 https://searchfox.org/mozilla-central/rev/da499aac682d0bbda5... (or at https://github.com/w3c/web-platform-tests/blob/a47dd526b9033f2ae56a0d81d5dd0aaf9c078979/fetch/api/headers/headers-record.html#L15 https://github.com/w3c/web-platform-tests/blob/a47dd526b9033... depending on which of these stays up more permanently).