The Symbol.isConcatSpreadable static data property represents the well-known symbol Symbol.isConcatSpreadable. The Array.prototype.concat() method looks up this symbol on each object being concatenated to determine if it should be treated as an array-like object and flattened to its array elements.

The Symbol.species static data property represents the well-known symbol Symbol.species. Methods that create copies of an object may look up this symbol on the object for the constructor function to use when creating the copy.

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The Symbol.unscopables static data property represents the well-known symbol Symbol.unscopables. The with statement looks up this symbol on the scope object for a property containing a collection of properties that should not become bindings within the with environment.

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The toHex() method of Uint8Array instances returns a hex-encoded string based on the data in this Uint8Array object.

The toPlainTime() method of Temporal.ZonedDateTime instances returns a new Temporal.PlainTime object representing the time portion of this date-time.

The until() method of Temporal.PlainTime instances returns a new Temporal.Duration object representing the duration from this time to another time (in a form convertible by Temporal.PlainTime.from()). The duration is positive if the other time is after this time, and negative if before.