Function select

src/patterns.ts:696–732

(
  ...args: [keyOrPattern?: unknown | string, pattern?: unknown]
)

  pattern: pattern
): Chainable<SelectP<k, input, pattern>, 'select' | 'or' | 'and'>;
export function select(
  ...args: [keyOrPattern?: unknown | string, pattern?: unknown]
): Chainable<SelectP<string>, 'select' | 'or' | 'and'> {
  const key: string | undefined =
    typeof args[0] === 'string' ? args[0] : undefined;
  const pattern: unknown =
    args.length === 2
      ? args[1]
      : typeof args[0] === 'string'
      ? undefined
      : args[0];
  return chainable({
    [matcher]() {
      return {
        match: (value) => {
          let selections: Record<string, unknown> = {
            [key ?? symbols.anonymousSelectKey]: value,
          };
          const selector = (key: string, value: any) => {
            selections[key] = value;
          };
          return {
            matched:
              pattern === undefined
                ? true
                : matchPattern(pattern, value, selector),
            selections: selections,
          };
        },
        getSelectionKeys: () =>
          [key ?? symbols.anonymousSelectKey].concat(
            pattern === undefined ? [] : getSelectionKeys(pattern)
          ),
      };
    },
  });
}

function isUnknown(x: unknown): x is unknown {
  return true;