Add CSRF to axios

app.js

/**
 * Next we will register the CSRF Token as a common header with Axios so that
 * all outgoing HTTP requests automatically have it attached. This is just
 * a simple convenience so we don't have to attach every token manually.
 */

const token = document.head.querySelector( 'meta[name="csrf-token"]' );
if ( token ) {
    window.axios.defaults.headers.common['X-CSRF-TOKEN'] = token.content;
} else {
    console.error( 'CSRF token not found: https://laravel.com/docs/csrf#csrf-x-csrf-token' );
}