Node.js streams => Delete contents of folder before transpiling to it - node.js

Question

I am using Gulp and I would like to delete/"clean" all contents of a directory before writing transpiled source to it.
Is there a way to connect the stream that runs the delete operation to the stream that does the read/transform/write operation?
Right now I have this:
function transpileJSX() {
var d = domain.create();
d.run(function () {
gulp.src('./public/static/app/js/views/**/*.js').pipe(react({harmony: true}))
.pipe(gulp.dest('./public/static/app/js/jsx')).on('end', function () {
d.emit('end');
d.exit();
});
});
return d;
}
function deleteJSX() {
return gulp.src('./public/static/app/js/jsx/**/*.js')
.pipe(clean({force: true}));
}
gulp.task('transpile-jsx', function () {
return transpileJSX().on('error', function (err) {
console.error(err);
});
});
gulp.task('delete-jsx', function (cb) {
return deleteJSX();
});
the problem is that this doesn't seem to work:
deleteJSX().pipe(transpileJSX());
the transpileJSX operation seems to start before the deleteJSX operation begins. And that might be expected when it comes to streams. But I think I want to make sure the whole thing works properly by ensuring the entire delete operation completes first?
For example, if I do this:
gulp.task('some-task', ['delete-jsx','transpile-jsx'], function (done) {
someTask(done);
});
the gulp logs show that the transpile-jsx task starts before the delete-jsx task ends.
If someone has a pattern to use when it comes to cleaning out a folder before transpiling to it, I'd like to copy it thanks!

Answer 1

You're almost there already. You just have to rearrange task dependencies, since gulp runs tasks for maximum concurrency:
gulp.task('transpile-jsx', ['delete-jsx'], function () {
//...
});
gulp.task('some-task', ['transpile-jsx'], function () {
//...
});
This will be easier once Gulp 4 hits. There you will be able to write stuff like:
gulp.task('some-task', gulp.series('delete-jsx', 'transpile-jsx', function () {
//...
}));