In the latest version 3.5.1
of Bitcoin and Altcoin Wallets you can now write JavaScript code that executes on some wallets-related event.
For example, you could choose to set the default coin, once the coin information is loaded from the JSON API. Do this like so:
jQuery( 'body' ).on( 'wallets_ready', function( event, coins, nonces ) { if ( 'object' === typeof coins.BTC ) { wp.wallets.viewModels.wallets.selectedCoin('BTC'); } } );There are full instructions on this in the documentation, under the Section Frontend → Frontend UI JavaScript event bindings. The documentation lists all of the available events, and sample code on how to enqueue your JavaScript file using wp_enqueue_script().