Planned lessonJNR-020-L03

Representing money, dates, and enums

On This Lesson 4 topics

This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.

In this lesson

pick formats that never lose information.

Money: never double or float (rounding errors). Use integer minor units (priceCents) or a decimal string, plus a currency code.
Dates and times: ISO 8601 with an offset or UTC, for example 2026-03-01T10:15:30Z. A time without an offset is ambiguous.
Enums: send stable uppercase strings ("SHIPPED"), not ordinal numbers; document the allowed values.
Use the same formats in requests and responses.
Unknown enum values from the client should give 400.

Draft outline details

json

{ "total": { "amount": 1999, "currency": "SAR" },
  "createdAt": "2026-03-01T10:15:30Z",
  "status": "SHIPPED" }

Why not 0.1 + 0.2 for money?

Show answer

Floating point cannot represent it exactly.

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