What could be causing the compilation error?

Question

gulp.js

When processing multiple js files, gulp throws an error
gulp-uglifyjs - UglifyJS threw an error
Unexpected token: operator (>)
internal/streams/legacy.js:59
throw er; // Unhandled stream error in pipe.
Here is the gulpfile itself

gulp.task('scripts', function() {
  return gulp.src([
    'js/1.js',
    'js/2.js',
                'js/3.js',
    ])
    .pipe(concat('libs.min.js')) 
    .pipe(uglify())
    .pipe(gulp.dest('/dist/js'));
});