Javascript tokenizeCard it的回调函数'；它不在Braintree上

我一直在将Braintree与我的应用程序集成，发现了一个问题。我需要使用tokenizeCard方法，但它似乎没有调用回调，我不明白为什么

function buyNow() {
    var token = getSessionVarFromView('client_token_braintree');
    console.error(token);
    braintree.setup(token, "custom", {id: "braintreePaymentForm"});
    var client = new braintree.api.Client({clientToken: token});
    client.tokenizeCard({number: "4111111111111111", expirationDate: "10/20"}, function (err, nonce) {
       console.error("On tokenize card");
    });
}

我的表格是这样的：

      <form method="POST" name="braintreePaymentForm" id="braintreePaymentForm">
                <div class='form-row'>
                  <div class='col-xs-8 form-group required'>
                    <label class='control-label'>Card number</label>
                    <input class='form-control' size="20" autocomplete="off" data-braintree-name="number">
                  </div>
                  <div class='col-xs-4 form-group required'>
                    <label class='control-label'>Security Code</label>
                    <input class='form-control' size="20" autocomplete="off" data-braintree-name="cvv">
                  </div>
                </div>
                <div class='form-row'>
                  <div class='col-xs-6 form-group required'>
                    <label class='control-label'>Name on card</label>
                    <input class='form-control' size="20" autocomplete="off" data-braintree-name="name_on_card">
                  </div>
                  <div class='col-xs-3 form-group required'>
                    <label class='control-label'>Expires on</label>
                    <input class='form-control' size="20" autocomplete="off" data-braintree-name="expiration_month">
                  </div>
                  <div class='col-xs-3 form-group required'>
                    <input class='form-control' size="20" autocomplete="off" data-braintree-name="expiration_year">
                  </div>
                </div>
                  <div id="buyNowBtn">
                </div>
            </form>

在此之后，永远不会调用tokenizeCard的回调函数

我希望有人能帮助我

谢谢

我在Braintree工作。如果您还有其他问题，您可以随时提问

---

表单提交按钮需要是

或

才能正确触发回调。您正在使用

只是想知道，您是否设置了Braintree javascript SDK？是的，我用那个部分更新了问题

Braintree_Configuration::environment('sandbox');
Braintree_Configuration::merchantId('merchantId');
Braintree_Configuration::publicKey('publicKey');
Braintree_Configuration::privateKey('privateKey');  

$clientToken = Braintree_ClientToken::generate();
return $clientToken;