Ok, I found it, just join $window , and you're done.
As written here: https://developers.braintreepayments.com/javascript+node/sdk/client/setup
"The SDK will be displayed as a dialog in the global window object. "
So, from your controller (for example) you can just use $window.braintree , and you have everything you need from the Braintree client library.
To download Dropin, you can simply use this:
angular.module('app').controller('YourController', ['$scope', '$window', function ($scope, $window) { $window.braintree.setup('CLIENTTOKEN', 'dropin', { container: 'dropin' }); } ]);
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