sweetalert.js uses the global swal in both version 1.*.* and version 2.*.* of its library. Therefore if you load both js/sweetalert.min.js and js/sweetalert-latest.min.js the first one to define the global swal will be used, the second will be ignored or cause a console error.

To prevent this only load one library such as:

// PHP
wp_enqueue_script( \'sweet-alert-latest\', plugin_dir_url( __FILE__ ) . \'js/sweetalert-latest.min.js\', array(), $this->version, false );

And update any references targeting old SweetAlert code according to the migration documentation

Alternatively If you want to use both libraries concurrently you could utilise ES6 modules with a compiler such as babel

// Javascript
import swal as oldswal from \'/my-local-js-directory/sweetalert.1.5.1.js\';
import swal as newswal from \'/my-local-js-directory/sweetalert.2.1.0.js\';

// Old alert
oldswal({
  // Old alert config here
});

// New alert
newswal({
  // New alert config here
});

Ref: Babel

With common JS you could do something like this

const oldswal = require(\'/my-local-js-directory/sweetalert.1.5.1.js\')
const newswal = require(\'/my-local-js-directory/sweetalert.2.1.0.js\')