The configuration variables related to your app are stored in /assets/custom/js/config.js file.
You can store configuration variables such as API keys related to third-party services inside this file.
The example structure of storing variables is —
window.config.facebook {
appId: '12345679098765431'
You can access these variables from inside JavaScript or from inside the HTML template.
// Accessing from inside JavaScript
// Or you can also access this way, once your app is initialized.
console.log(; // This is the recommended way
<!-- Accessing from inside HTML template -->
<div>{$f7.config.facebook.appId}}</div> <!-- After parsing, the output will be 12345679098765431 -->