Develop Reference

Gulp - TypeError: is not a function. How search key of problem?

gulp file code:
let preprocessor = 'sass';
const {app, dest, parallel, watch} = require('gulp'),
browserSync = require('browser-sync').create(),
concat = require('gulp-concat'),
uglify = require('gulp-uglify-es').default(),
sass = require('gulp-sass'),
autoprefixer = require('gulp-autoprefixer'),
cleancss = require('gulp-clean-css'),
imagemin = require('gulp-imagemin'),
newer = require('gulp-newer'),
del = require('del');
function browsersync() {
browserSync.init({
server: {'baseDir': 'src/'},
notify: false,
online: true
});
}
function scripts() {
return app([
'src/js/script.js'
])
.pipe(concat('script.min.js'))
.pipe(uglify())
.pipe(dest('src/js/'))
.pipe(browserSync.stream());
}
function startwatch() {
watch(['src/**/*.js', '!src/**/*.min.js'], scripts);
watch('src/**/' + preprocessor + '/**/*', styles);
watch('src/**/*.html').on('change', browserSync.reload);
watch('src/images/**/*', images);
}
function styles() {
return app('src/' + preprocessor + '/style.' + preprocessor + '')
.pipe(eval(preprocessor)())
.pipe(concat('style.min.css'))
.pipe(autoprefixer({ overrideBrowserslist: ['last 10 versions'], grid: true }))
.pipe(cleancss( { level: { 1: { specialComments: 0 } }} ))
.pipe(dest('src/css/'))
.pipe(browserSync.stream());
}
function images() {
return app('src/images/**/*')
.pipe(newer('src/images'))
.pipe(imagemin())
.pipe(dest('src/images'));
}
function cleanimg() {
return del('src/images/**/*', { force: true });
}
exports.browsersync = browsersync;
exports.scripts = scripts;
exports.styles = styles;
exports.images = images;
exports.cleanimg = cleanimg;
exports.default = parallel(styles, scripts, browsersync, startwatch);
Result:
[21:41:22] 'styles' errored after 38 ms
[21:41:22] TypeError: app is not a function
at styles (C:\Users\vladi\Desktop\projects\Web\nextPr\gulpfile.js:42:9)
at bound (domain.js:413:15)
at runBound (domain.js:424:12)
at asyncRunner (C:\Users\vladi\Desktop\projects\Web\nextPr\node_modules\async-done\index.js:55:18)
at processTicksAndRejections (internal/process/task_queues.js:75:11)
[21:41:22] 'default' errored after 70 ms
Explain why there is a problem I cannot understand.
I have already crawled all over google and could not find a solution to this problem.
I would be very grateful if you can help.
I partially took this code from the Internet, but did not find a solution to this question.
I am new to web development and it is still difficult for me to navigate. I can't find a person who could tell me or direct me in the right direction.

Change this line:
const {app, dest, parallel, watch} = require('gulp'),
to
const {src, dest, parallel, watch} = require('gulp'),
I don't know where the app came from but there is no exported app from gulp.
And then change all your references to app, like:
return app('src/' + preprocessor + '/style.' + preprocessor + '')
to
return src('src/' + preprocessor + '/style.' + preprocessor + '')

For the next time - the error tells you exactly on which line the problem is. You'll eventually learn to understand certain types of errors - e.g. "something is not a function" means you're using something as a function, but it's not that (maybe it's a different type, maybe it's even not defined - such as in this case).
This would lead you to look at "app()". Why is it not a function?
If you're using external library - it usually has a documentation you can go through.
In this case you'd find there's nothing about "app" in there. You'd also find better examples than the one you copied from who knows where.

How to make Gulp watch monitoring files?

I have a simple gulpfile.js, that defines only two tasks, buildLess and watchFiles:
var gulp = require('gulp');
var less = require('gulp-less');
var watch = require('gulp-watch');
var plumber = require('gulp-plumber');
var filter = require('gulp-filter');
function buildLess(done) {
const fileFilter = filter(['**/*', '!**/mixins.less', '!**/variables.less']);
gulp.src('./public/less/*.less')
.pipe(fileFilter)
.pipe(plumber())
.pipe(less())
.pipe(gulp.dest('./public/css/'))
;
done();
};
function watchFiles() {
gulp.watch(['public/less/*.less'], gulp.series('build-less'));
// gulp.watch(['./public/less/*.less'], gulp.series(buildLess));
};
gulp.task('build-less', buildLess);
gulp.task('watch-files', watchFiles);
The first one ($ gulp build-less) is working fine. The watchFiles ($ gulp watch-files) can be started and doesn't cause any errors, but changes on the public/less/style.less are ignored.
What is wrong at this gulpfile.js and how to get the watch-files task working?

The gulp.series API allows you to pass a string of a previously registered task. In your code, you haven't registered build-less yet.
var gulp = require('gulp');
var less = require('gulp-less');
var watch = require('gulp-watch');
var plumber = require('gulp-plumber');
var filter = require('gulp-filter');
function buildLess(done) {
const fileFilter = filter(['**/*', '!**/mixins.less', '!**/variables.less']);
gulp.src('./public/less/*.less')
.pipe(fileFilter)
.pipe(plumber())
.pipe(less())
.pipe(gulp.dest('./public/css/'))
;
done();
};
gulp.task('build-less', buildLess);
function watchFiles() {
gulp.watch(['public/less/*.less'], gulp.series('build-less'));
// gulp.watch(['./public/less/*.less'], gulp.series(buildLess));
};
gulp.task('watch-files', watchFiles);
I would note that Gulp does not recommend using the gulp.task API anymore to register tasks, but instead to use exports.
Secondly, you don't need gulp-watch, as gulp now comes with its own gulp.watch method (which you are already using).
Lastly, you should make sure to your correctly signaling async completion in your buildLess function. Below, I've changed that function to return a Stream, rather than calling a done() callback since as you have it written, you have a race condition where done() may be called before the Less compilation has finished.
var gulp = require('gulp');
var less = require('gulp-less');
var plumber = require('gulp-plumber');
var filter = require('gulp-filter');
function buildLess() {
const fileFilter = filter(['**/*', '!**/mixins.less', '!**/variables.less']);
return gulp
.src('./public/less/*.less')
.pipe(fileFilter)
.pipe(plumber())
.pipe(less())
.pipe(gulp.dest('./public/css/'));
}
exports['build-less'] = buildLess;
function watchFiles() {
gulp.watch(['public/less/*.less'], buildLess);
}
exports['watch-files'] = watchFiles;
Overall, I'd go through Gulp's documentation. They recently updated their website, and updated their documentation along with it. Going through that might clear up some other questions you may be having.

Gulp 4.0: gulp-remember or gulp-cache prevent sass to compile properly (Incremental build)

yesterday I've upgraded my Gulp to 4.0 in order to gain some speed while compiling styles for my project (they got big, right now on my Mac Pro 2016 I need to wait 19seconds)
After some digging I decided to add gulp-cached and gulp-remember to my build.
Here's my current gulpfile.js for the styles:
var gulp = require('gulp'),
sass = require('gulp-sass'),
cached = require('gulp-cached'),
sourcemaps = require('gulp-sourcemaps'),
autoprefixer = require('gulp-autoprefixer'),
remember = require('gulp-remember'),
gs = gulp.series,
concat = require('gulp-concat'),
gp = gulp.parallel;
gulp.task('compile:styles', () => {
return gulp.src([
// Grab your custom scripts
'./assets/scss/**/*.scss'
])
.pipe(sourcemaps.init()) // Start Sourcemaps
.pipe(cached('sass'))
.pipe(sass())
.pipe(autoprefixer({
browsers: ['last 2 versions']
}))
.pipe(remember('sass'))
.pipe(sourcemaps.write('.')) // Creates sourcemaps for minified styles
.pipe(gulp.dest('./assets/css/'));
});
gulp.task('watch:styles', () => {
gulp.watch('./assets/scss/**/*.scss', gs('styles'))
.on('change', function (event) {
console.log("event happened:"+JSON.stringify(event));
if (event.type === 'deleted') {
//delete from gulp-remember cache
remember.forget('sass', event.path);
//delete from gulp-cached cache
delete cache.caches['sass'][event.path];
}
});
});
gulp.task('watch', gp(
'watch:styles'
));
My issue here is that my build works well on first compilation which takes about 3 seconds, later on where ever I do a change it can see in which file I made that change, and it starting to compile, but the output file does not have the changes inside.
I think I am not getting something when it comes to gulp-cached and gulp-remeber. But at the end of the file you can see a function that are supposed to clean the caches once a change was made.
Can you please take a look at my code? Maybe you will have some advice.
Cheers!
### EDIT 26.08
I have encountered the following post while looking for a solution:
http://blog.reactandbethankful.com/posts/2015/05/01/building-with-gulp-4-part-4-incremental-builds/
I went with it accordingly with the following code (but the effect is same as in above example):
// Grab our gulp packages
var gulp = require('gulp'),
sass = require('gulp-sass'),
sourcemaps = require('gulp-sourcemaps'),
autoprefixer = require('gulp-autoprefixer'),
gs = gulp.series,
gp = gulp.parallel,
cache = require('gulp-memory-cache');
gulp.task('compile:styles', () => {
return gulp.src('./assets/scss/**/*.scss', {since: cache.lastMtime('sass')})
.pipe(sourcemaps.init()) // Start Sourcemaps
.pipe(sass())
.pipe(autoprefixer({
browsers: ['last 2 versions']
}))
.pipe(cache('sass'))
.pipe(sourcemaps.write('.')) // Creates sourcemaps for minified styles
.pipe(gulp.dest('./assets/css/'));
});
gulp.task('watch:styles', () => {
gulp.watch('./assets/scss/**/*.scss', gs('compile:styles'))
.on('change', cache.update('sass'));
});
gulp.task('build', gs(
'compile:styles',
'watch:styles'
));

I have created a complete gulpfile.js here:
https://gist.github.com/MkBeeCtrl/5a6a0900dba1c5d42dc7b6da211b3e95
With js files compilation included.
// Grab our gulp packages
var gulp = require('gulp'),
sass = require('gulp-sass'),
sourcemaps = require('gulp-sourcemaps'),
autoprefixer = require('gulp-autoprefixer'),
gs = gulp.series,
gp = gulp.parallel,
cached = require('gulp-cached'),
dependents = require('gulp-dependents');
gulp.task('compile:styles', () => {
return gulp.src('./assets/scss/**/*.scss')
.pipe(cached('sass'))
.pipe(dependents())
.pipe(sourcemaps.init()) // Start Sourcemaps
.pipe(sass())
.pipe(autoprefixer({browsers: ['last 2 versions']}))
.pipe(sourcemaps.write('.')) // Creates sourcemaps for minified styles
.pipe(gulp.dest('./assets/css/'));
});
gulp.task('watch:styles', () => {
gulp.watch('./assets/scss/**/*.scss', gs('compile:styles'))
.on('change', function (event) {
console.log("event happened:"+JSON.stringify(event));
if (event.type === 'deleted') {
//delete from gulp-remember cache
//emember.forget('sass', event.path);
//delete from gulp-cached cache
delete cache.caches['sass'][event.path];
}
});
});
gulp.task('build', gs(
'compile:styles',
'watch:styles'
));
The above solution works the way I want, so if you want to produce separate CSS files from multiple imported files, you can go with it. It's not blazing fast solution but I have managed to save about 1 second when recompiling (already saved about 15s, when I started this topic, a build lasted 19 secs):
1st compile: ~3.5s
2nd or late: ~2.4s
You dont need to concate or order here as the whole order thing happens when you import scss files into you main file.

Try this one. I suppose it might do what you want to achieve:
'use strict';
const gulp = require('gulp');
const path = require('path');
const cached = require('gulp-cached');
const remember = require('gulp-remember');
const sass = require('gulp-sass');
const autoprefixer = require('gulp-autoprefixer');
const sourcemaps = require('gulp-sourcemaps');
const concat = require('gulp-concat');
gulp.task('styles:compile', function() {
return gulp.src('assets/scss/**/*.scss', {since: gulp.lastrun('styles:compile')})
.pipe(sourcemaps.init())
//.pipe(cached('sass')) - a smarter but heavier alternative to since
.pipe(remember('sass'))
.pipe(concat('all.sass'))
.pipe(sass())
.pipe(autoprefixer({ browsers: ['last 2 versions'] }))
.pipe(sourcemaps.write())
.pipe(gulp.dest('assets/css/'));
});
gulp.task('styles:watch', function() {
var watcher = gulp.watch('assets/scss/**/*.scss', gulp.series('compile:styles'));
watcher.on('unlink', function(filepath) {
remember.forget('sass', path.resolve(filepath));
//delete cached.caches.sass[path.resolve(filepath)];
});
});
gulp.task('default', gulp.series('styles:compile', 'styles:watch'));
Install path plugin to resolve paths. Use 'unlink' event if you want to detect when a file gets deleted. since just checks dates which is faster compared to cached that reads and compares content. But cached is more reliable (for example, when you deleted and then returned the file using your IDE tools since will not work since the file will be returned again with its old date). Also check paths - I might have messed them up.

How do you use browserify in a Gulp task?

I'm pretty new to Gulp, but by following this tutorial I set up a Gulp task that is meant to browserify javascript files in a particular directory and pipe them to a different directory - pretty simple. I've looked a few other tutorials, but this method seemed to be the most concise. Here is my code:
var gulp = require('gulp');
var browserify = require('browserify');
var transform = require('vinyl-transform');
gulp.task('js', function() {
var browserified = transform(function(filename) {
return browserify(filename).bundle();
});
return gulp.src(['./public/js/src/**/*.js'])
.pipe(browserified)
.pipe(gulp.dest('./public/js/dist'));
});
The above code is very similar to many other implementations of this sort I've seen, but when I try running it with gulp js, it produces the following error:
[15:47:13] Using gulp file
~/development/launchpad/workshop/gulpfile.js
[15:47:13] Starting 'js'...
_stream_readable.js:540
var ret = dest.write(chunk);
^
TypeError: undefined is not a function
at Producer.ondata (_stream_readable.js:540:20)
at Producer.emit (events.js:107:17)
at Producer.Readable.read (_stream_readable.js:373:10)
at flow (_stream_readable.js:750:26)
at resume_ (_stream_readable.js:730:3)
at _stream_readable.js:717:7
at process._tickCallback (node.js:355:11)
Does anyone know what might cause this error?
(As a side note, I'd like to look at the files from the stack trace to try to figure out what is going on here, but searching for _stream_readable.js in Spotlight yields about 20 files of that name, all seemingly Node modules. Is there a way to determine the full path of a file in a stack trace?)

var browserify = require('browserify');
var gulp = require('gulp');
var source = require('vinyl-source-stream');
gulp.task('browserify', function() {
return browserify('lib/front/app.js')
.bundle()
//Pass desired output filename to vinyl-source-stream
.pipe(source('bundle.js'))
// Start piping stream to tasks!
.pipe(gulp.dest('public/build/'));
});

If you want browserify to work with gulp. dest and create a file where we specify it via .pipe (gulp.dest ('src/js')),
then you need to download vinyl-source-stream and throw it in .pipe(source('bundle.js')),
but actually in browserify, namely the bundle method accepts callback and neither dest nor source is needed
browserify({
entries: jsFile,
basedir: "src/js/dev",
debug: true,
})
.transform(babelify, {
presets: ['#babel/preset-env'],
})
.bundle((err, buffer) => {
let event = new EventEmitter();
if (err) {
event.emit('error',err)
}
else {
let data = minify(buffer.toString(), {}).code;
fs.createWriteStream('./src/js/bundle.js').write(data)
console.dir(222);
bs.reload()
}
})

Unfortunately, this is an issue with browserify/gulp, and there's nothing that vinyl-transform can do. The solution is to use vinyl-source-stream and vinyl-buffer:
var gulp = require('gulp');
var browserify = require('browserify');
var source = require('vinyl-source-stream');
var glob = require('node-glob');
gulp.task('browserify', function (cb) {
glob('./src/**/*.js', {}, function (err, files) {
var b = browserify();
files.forEach(function (file) {
b.add(file);
});
b.bundle().
.pipe(source('output.js'))
.pipe(gulp.dest('./dist'));
cb();
})
});
More information here.

How to add a watch to a folder in gulp

I have the following glupfile.js, it works fine but I need to run the default gulp task when a files in folder.
How to change my script in order to support gulp watch?
var gulp = require('gulp');
var jscs = require('gulp-jscs');
var jshint = require('gulp-jshint');
var noop = function () { };
var stylish = require('gulp-jscs-stylish');
var folders = [
'./a/**/*.js',
'./b/**/*.js',
'./c/**/*.js',
'a.js',
'b.js',
'c.js',
'd.js'
];
gulp.task('default', function () {
gulp.src(folders)
.pipe(jshint()) // hint (optional)
.pipe(jscs()) // enforce style guide
.on('error', noop) // don't stop on error
.pipe(stylish.combineWithHintResults()) // combine with jshint results
.pipe(jshint.reporter('jshint-stylish')); // use any jshint reporter to log hint and style guide errors
});

Try adding a gulp task as given below
gulp.task('watch',function(){
gulp.watch(folders,['default']);
});
gulp.task('default',['watch']);
Basically it watches the folders for any change and if any change happens, it executes your default task.