How to use the crypto-browserify.createHmac function in crypto-browserify

* You may not use this file except in compliance with the
 * License. A copy of the License is located at
 *
 *     http://aws.amazon.com/asl/
 *
 * or in the "license" file accompanying this file. This file is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, express or implied. See the License
 * for the specific language governing permissions and
 * limitations under the License.
 */

import { Buffer } from 'buffer/';
//import createHmac from 'create-hmac';
import * as crypto from 'crypto-browserify';
var createHmac = crypto.createHmac;

import BigInteger from './BigInteger';
import AuthenticationHelper from './AuthenticationHelper';
import CognitoAccessToken from './CognitoAccessToken';
import CognitoIdToken from './CognitoIdToken';
import CognitoRefreshToken from './CognitoRefreshToken';
import CognitoUserSession from './CognitoUserSession';
import DateHelper from './DateHelper';
import CognitoUserAttribute from './CognitoUserAttribute';
import StorageHelper from './StorageHelper';

/**
 * @callback nodeCallback
 * @template T result
 * @param {*} err The operation failure reason, or null.
 * @param {T} result The operation result.

* You may not use this file except in compliance with the
 * License. A copy of the License is located at
 *
 *     http://aws.amazon.com/asl/
 *
 * or in the "license" file accompanying this file. This file is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, express or implied. See the License
 * for the specific language governing permissions and
 * limitations under the License.
 */

import { Buffer } from 'buffer/';
import * as crypto from 'crypto-browserify';
const createHash = crypto.createHash;
const createHmac = crypto.createHmac;
const randomBytes = crypto.randomBytes;

import BigInteger from './BigInteger';

const initN = 'FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1'
  + '29024E088A67CC74020BBEA63B139B22514A08798E3404DD'
  + 'EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245'
  + 'E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED'
  + 'EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3D'
  + 'C2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F'
  + '83655D23DCA3AD961C62F356208552BB9ED529077096966D'
  + '670C354E4ABC9804F1746C08CA18217C32905E462E36CE3B'
  + 'E39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9'
  + 'DE2BCBF6955817183995497CEA956AE515D2261898FA0510'
  + '15728E5A8AAAC42DAD33170D04507A33A85521ABDF1CBA64'
  + 'ECFB850458DBEF0A8AEA71575D060C7DB3970F85A6E1E4C7'

* You may not use this file except in compliance with the
 * License. A copy of the License is located at
 *
 *     http://aws.amazon.com/asl/
 *
 * or in the "license" file accompanying this file. This file is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, express or implied. See the License
 * for the specific language governing permissions and
 * limitations under the License.
 */

import { Buffer } from 'buffer/';
//import createHmac from 'create-hmac';
import * as crypto from 'crypto-browserify';
const createHmac = crypto.createHmac;

import BigInteger from './BigInteger';
import AuthenticationHelper from './AuthenticationHelper';
import CognitoAccessToken from './CognitoAccessToken';
import CognitoIdToken from './CognitoIdToken';
import CognitoRefreshToken from './CognitoRefreshToken';
import CognitoUserSession from './CognitoUserSession';
import DateHelper from './DateHelper';
import CognitoUserAttribute from './CognitoUserAttribute';
import StorageHelper from './StorageHelper';

/**
 * @callback nodeCallback
 * @template T result
 * @param {*} err The operation failure reason, or null.
 * @param {T} result The operation result.

function encodeSign(str, key) {
	return crypto
		.createHmac('sha1', key)
		.update(str)
		.digest('base64')
		.replace(/\//g, '_')
		.replace(/\+/g, '-');
}