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typeGuards

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typeGuards exposes reusable runtime predicates that help you narrow unknown values safely.

import {typeGuards} from '@livon/schema';

interface MessagePayload {
  author: string;
  text: string;
}

const isMessagePayload = (input: unknown): input is MessagePayload =>
  typeGuards.isRecord(input) &&
  typeGuards.isString(input.author) &&
  typeGuards.isString(input.text);

const parsePayload = (input: unknown): MessagePayload => {
  if (!isMessagePayload(input)) {
    throw new Error('Invalid payload');
  }
  return input;
};

Parameters​

isMessagePayload(input):

  • input (unknown): value to narrow.

parsePayload(input):

  • input (unknown): runtime payload checked via type guards before returning typed value.

Available guards:

  • isString
  • isNumber
  • isBoolean
  • isDate
  • isUint8Array
  • isRecord
  • isArray