How to use the braintree-web/client.create function in braintree-web

function initHostedFields() {
    client.create({ authorization: braintreeParams.token }, function (
      clientErr,
      clientInstance
    ) {
      if (clientErr) {
        showErrorMessage(loadingErrorMsg);
        return;
      }

      dataCollector.create({ client: clientInstance, kount: true }, function (
        clientErr,
        dataCollectorInstance
      ) {
        if (clientErr) {
          showErrorMessage(loadingErrorMsg);
          return;
        }

setAuthorization(authorization, onAuthorizationSuccess) {
        if (!authorization && this.authorization) {
            this.teardown();
        } else if (authorization && authorization !== this.authorization) {
            if (this.authorization) { this.teardown(); }
            this.authorization = authorization;
            Braintree.create({ authorization }, (err, clientInstance) => {
                if (err) {
                    this.onError(err);
                } else {
                    this.create(clientInstance, onAuthorizationSuccess);

                    if (this.wrapperHandlers.onDataCollectorInstanceReady) {
                        BraintreeDataCollector.create({
                            client: clientInstance,
                            kount: true,
                        }, this.wrapperHandlers.onDataCollectorInstanceReady);
                    }
                }
            });
        }
    }

fetchEnv((envData) => {
    let currency = getCurrency().toLowerCase();
    client.create({ authorization: braintreeParams.token }, function (
      clientErr,
      clientInstance
    ) {
      if (clientErr) {
        showErrorMessage(loadingErrorMsg);
        return;
      }

      paypalCreate(
        {
          client: clientInstance,
          merchantAccountId: envData.BRAINTREE_MERCHANT_ACCOUNTS[currency],
        },
        function (paypalCheckoutErr, paypalCheckoutInstance) {
          if (paypalCheckoutErr) {
            showErrorMessage(loadingErrorMsg);

function create(options) {
  if (!options.authorization) {
    return Promise.reject(new DropinError('options.authorization is required.'));
  }

  return client.create({
    authorization: options.authorization
  }).catch(function (err) {
    return Promise.reject(new DropinError({
      message: 'There was an error creating Drop-in.',
      braintreeWebError: err
    }));
  }).then(function (clientInstance) {
    clientInstance = setAnalyticsIntegration(clientInstance);

    if (clientInstance.getConfiguration().authorizationType === 'TOKENIZATION_KEY') {
      analytics.sendEvent(clientInstance, 'started.tokenization-key');
    } else {
      analytics.sendEvent(clientInstance, 'started.client-token');
    }

    return new Promise(function (resolve, reject) {