Gulp Watch only run once

Question

I'm using this Gulp Watch sample: https://github.com/floatdrop/gulp-watch/blob/master/docs/readme.md#starting-tasks-on-events.

var gulp = require('gulp');
var watch = require('gulp-watch');
var batch = require('gulp-batch');

gulp.task('build', function () { console.log('Working!'); });

gulp.task('watch', function () {
    watch('**/*.js', batch(function () {
        gulp.start('build');
    }));
});

When I run it on my Windows 8 machine, it only runs the first time I change a file:

C:\test>gulp watch
[08:40:21] Using gulpfile C:\test\gulpfile.js
[08:40:21] Starting 'watch'...
[08:40:21] Finished 'watch' after 2.69 ms
[08:40:31] Starting 'build'...
Working!
[08:40:31] Finished 'build' after 261 µs

Next time nothing happens. Why?

Answer 1

If you read the documentation closely, you see the following phrase:

You can pass plain callback, that will be called on every event or wrap it in gulp-batch to run it once

So, that's basically the deal with gulp-batch. To constantly watch it, just remove the batch call:

gulp.task('build', function (done) { 
    console.log('Working!'); 
    done();
});

gulp.task('watch', function () {
    watch('app/*.js', function () {
        gulp.start('build');
    });
});

(and add the 'done' callback to build to let Gulp know when you're finished).

Btw... I'm not sure, but I think gulp-watch is meant to not only watch files, but also directly returning a vinyl object. So actually using the built-in gulp.watch should have the same effect:

gulp.task('watch', function () {
    gulp.watch('app/**/*.js', ['build']);
});