How to use the laravel-mix.mix.version function in laravel-mix

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel application. By default, we are compiling the Sass
 | file for the application as well as bundling up all the JS files.
 |
 */

mix.options({ processCssUrls: false });

// versions
mix.version([
    'public/assets/js/vendor.js',
    'public/assets/js/mobile.main.js',
    'public/assets/js/console.main.js',
    'public/assets/js/app.main.js',
    'public/assets/css/app.main.css',
    'public/assets/css/console.main.css',
    'public/assets/css/mobile.main.css',
    'public/assets/js/manifest.js',
    'public/assets/css/app.vendor.css',
    'public/assets/css/console.vendor.css',
    'public/assets/css/mobile.vendor.css',
    'public/assets/js/app.vendor.js',
    'public/assets/js/console.vendor.js',
    'public/assets/js/mobile.vendor.js',
    'public/assets/css/app.theme.css',
    'public/assets/js/app.theme.js',

'resources/assets/css/pratt_landing.min.css'
   ], 'public/css/all-landing.css')
   // PACKAGE (ADMINLTE-LARAVEL) RESOURCES
   .copy('resources/assets/img/*.*','public/img/')
   //VENDOR RESOURCES
   .copy('node_modules/font-awesome/fonts/*.*','public/fonts/')
   .copy('node_modules/ionicons/dist/fonts/*.*','public/fonts/')
   .copy('node_modules/bootstrap/fonts/*.*','public/fonts/')
   .copy('node_modules/admin-lte/dist/css/skins/*.*','public/css/skins')
   .copy('node_modules/admin-lte/dist/img','public/img')
   .copy('node_modules/admin-lte/plugins','public/plugins')
   .copy('node_modules/icheck/skins/square/blue.png','public/css')
   .copy('node_modules/icheck/skins/square/blue@2x.png','public/css');

if (mix.config.inProduction) {
  mix.version();
  mix.minify();
}

* We Extract Vendor Script see: packages.json
 */
   .extract(['vue', 'lodash', 'axios', 'vue-router', 'moment', 'vuex', 'vuex-router-sync', 'vee-validate'])
/*
 * Load Our App Styling
 */
  //  .sass('resources/assets/sass/app.scss', 'public/css')
/*
 * Load SourceMap For Extra Debugging Feature in Development
 */
   .sourceMaps()
/*
 * Version Our Script Only if Production
 */
if (mix.config.inProduction) {
  mix.version()
}
/*
 * Disable Notifications
 */
mix.disableNotifications()

} else {
    var publicPath = "../../../public/vendor/webkul/preorder/assets";
}

mix.setPublicPath(publicPath).mergeManifest();
mix.disableNotifications();

mix.copyDirectory(__dirname + "/src/Resources/assets/images", publicPath + "/images")
    .sass(__dirname + "/src/Resources/assets/sass/app.scss", "css/preorder.css")
    .sass(__dirname + "/src/Resources/assets/sass/admin.scss", "css/preorder-admin.css")
    .options({
        processCssUrls: false
    });

if (mix.inProduction()) {
    mix.version();
}

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel application. By default, we are compiling the Sass
 | file for the application as well as bundling up all the JS files.
 |
 */

mix.js('resources/assets/js/app.js', 'public/js')
   .sass('resources/assets/sass/app.scss', 'public/css');

if (mix.config.inProduction) {
	mix.version();
}

mix.disableNotifications();

mix.copyDirectory(__dirname + "/src/Resources/assets/images", publicPath + "/images")
    .sass(__dirname + "/src/Resources/assets/sass/default.scss", "css/default-booking.css")
    .sass(__dirname + "/src/Resources/assets/sass/velocity.scss", "css/velocity-booking.css")
    .options({
        processCssUrls: false
    });


if (! mix.inProduction()) {
    mix.sourceMaps();
}

if (mix.inProduction()) {
    mix.version();
}

__dirname + '/src/Resources/assets/sass/admin.scss',
        __dirname + '/' + publicPath + '/css/velocity-admin.css'
    )
    .sass(
        __dirname + '/src/Resources/assets/sass/app.scss',
        __dirname + '/' + publicPath + '/css/velocity.css', {
            includePaths: ['node_modules/bootstrap-sass/assets/stylesheets/'],
        }
    )

    .options({
        processCssUrls: false
    });

if (mix.inProduction()) {
    mix.version();
}

/*
 * Builds sources maps for assets.
 *
 * @link https://laravel.com/docs/5.6/mix#css-source-maps
 */
mix.sourceMaps();

/*
 * Versioning and cache busting. Append a unique hash for production assets. If
 * you only want versioned assets in production, do a conditional check for
 * `mix.inProduction()`.
 *
 * @link https://laravel.com/docs/5.6/mix#versioning-and-cache-busting
 */
mix.version();

/*
 * Ripped straight from the repos of Justin Tadlock
 * @link https://github.com/justintadlock/mythic/blob/master/webpack.mix.js
 * 
 * Add custom Webpack configuration.
 *
 * Laravel Mix doesn't currently minimize images while using its `.copy()`
 * function, so we're using the `CopyWebpackPlugin` for processing and copying
 * images into the distribution folder.
 *
 * @link https://laravel.com/docs/5.6/mix#custom-webpack-configuration
 * @link https://webpack.js.org/configuration/
 */
mix.webpackConfig( {
	stats       : 'minimal',

},
    resolve:{
        alias: {
            'vue-router$': 'vue-router/dist/vue-router.common.js'
        }
    }
});

mix.js('resources/assets/js/app.js', 'public/js')
   .sass('resources/assets/sass/app.scss', 'public/css')
   .js('resources/assets/admin/admin.js', 'public/js')
   .extract(['vue', 'axios', 'vue-router'])
   .sass('resources/assets/admin/admin.scss', 'public/css');

if (mix.config.inProduction) {
    mix.version();
}