@polkadot/util/is/hex.js

A collection of useful utilities for @polkadot

// Copyright 2017-2022 @polkadot/util authors & contributors
// SPDX-License-Identifier: Apache-2.0
export const REGEX_HEX_PREFIXED = /^0x[\da-fA-F]+$/;
export const REGEX_HEX_NOPREFIX = /^[\da-fA-F]+$/;
/**
 * @name isHex
 * @summary Tests for a hex string.
 * @description
 * Checks to see if the input value is a `0x` prefixed hex string. Optionally (`bitLength` !== -1) checks to see if the bitLength is correct.
 * @example
 * <BR>
 *
 * ```javascript
 * import { isHex } from '@polkadot/util';
 *
 * isHex('0x1234'); // => true
 * isHex('0x1234', 8); // => false
 * ```
 */

export function isHex(value, bitLength = -1, ignoreLength) {
  return typeof value === 'string' && (value === '0x' || REGEX_HEX_PREFIXED.test(value)) && (bitLength === -1 ? ignoreLength || value.length % 2 === 0 : value.length === 2 + Math.ceil(bitLength / 4));
}