@maplibre/maplibre-gl-style-spec/src/validate/validate_enum.ts

a specification for maplibre styles

import {ValidationError} from '../error/validation_error';
import {unbundle} from '../util/unbundle_jsonlint';

export function validateEnum(options) {
    const key = options.key;
    const value = options.value;
    const valueSpec = options.valueSpec;
    const errors = [];

    if (Array.isArray(valueSpec.values)) {
        // <=v7
        if (valueSpec.values.indexOf(unbundle(value)) === -1) {
            errors.push(
                new ValidationError(
                    key,
                    value,
                    `expected one of [${valueSpec.values.join(', ')}], ${JSON.stringify(value)} found`
                )
            );
        }
    } else {
        // >=v8
        if (Object.keys(valueSpec.values).indexOf(unbundle(value) as string) === -1) {
            errors.push(
                new ValidationError(
                    key,
                    value,
                    `expected one of [${Object.keys(valueSpec.values).join(', ')}], ${JSON.stringify(value)} found`
                )
            );
        }
    }
    return errors;
}