Skip to main content
Dublin Library

The Publishing Project

Passing flags and arguments to Gulp


There are times when we want to do different things based on whether we're creating code for production or development.

This is based on the example from the Gulp documentation. We'll use this as the base and then see if we can expand it further.

As with all Gulp projects we use NPM to install the packages we want to use

npm install -D gulp gulp-if \
gulp-uglify yargs

Then we requite the packages. We're not using modules for this example.

const gulp = require('gulp');
const gulpif = require('gulp-if');
const uglify = require('gulp-uglify');
const args = require('yargs').argv;

We then set the different options we want to control. In this case, we create an env const and make the value either the value of the NODE_ENV variable or development if we don't add a value in the command line.

const env = args.env ? process.env.NODE_ENV : 'development';

The task uses gulp-if to test if we asked for a production environment (if arg.env is production) and uglifies the scripts if we did.

gulp.task('scripts', function() {
  return gulp.src('./src/js/**/*')
     // only minify in production
     .pipe(gulpif(args.env === 'production', uglify()))

The following Bash command will produce uglified script output.

gulp scripts --env production

We could add other flags to add conditions elsewhere in the build file. For example, if we use SASS or other CSS preprocessors, we could use the same technique to only produce compressed output or generate sourcemaps for production.

Edit on Github