gulp_vendor_js

var concat = require('gulp-concat');    //Add dependency to package.json if not added  
 
gulp.task('vendor-js', function () {
 gulp.src(["assets/js/sweetalert2.min.js","assets/js/jquery-ui.min.js'" ... ])  // Add all js files path
 .pipe(concat('vendor.js'))                                                     //Concatenate to a single js file
 .pipe(gulp.dest('dist/prod/src/assets/js/'));                                  // destination folder
});