Enumerated values

The enum keyword in JSON Schema allows you to restrict a value to a set of predefined options. It requires an array with at least one unique element, and any value validated against this schema must exactly match one of the specified values.

Below are several examples demonstrating its usage.

Basic Example: Street Light Colors

This example demonstrates how to validate that the color property of a street light is either "red", "amber", or "green".

schema

{ "properties": { "color": { "enum": ["red", "amber", "green"] } }}

data

{ "color": "red" }

compliant to schema

data

{ "color": "blue" }

not compliant to schema

Extended Example: Accepting Multiple Data Types

Enums can be used without explicitly setting a data type, allowing different types of values. In the following example, the schema is extended to include null (to represent an "off" state) and the number 42.

schema

{ "properties": { "color": { "enum": ["red", "amber", "green", null, 42] } }}

data

{ "color": null }

compliant to schema

data

{ "color": 42 }

compliant to schema

data

{ "color": 0 }

not compliant to schema

Additional Example: Mixed Types for Shape

schema

{ "properties": { "shape": { "enum": ["circle", "square", 1, null] } }}

data

{ "shape": "circle" }

compliant to schema

data

{ "shape": 1 }

compliant to schema

data

{ "shape": null }

compliant to schema

data

{ "shape": "triangle" }

not compliant to schema