问gulp-babel将es6更改为es5要求不是未定义的

EN

gulp.task('es6', function() {
    gulp.src('libs/es6/*.js')
    .pipe(babel())
    .pipe(gulp.dest('libs/js'))
        .pipe(concat('all.js'))
        .pipe(gulp.dest('libs/dist'))
        .pipe(rename('all.min.js'))
        .pipe(uglify())
        .pipe(gulp.dest('libs/dist'));
});

{
  "presets": ["es2015"]
}

{
  "presets": ["es2015"],
  "plugins": ["babel-plugin-transform-es2015-modules-amd"]
}