Bootswatch and Gulp as a Stepping Stone for Your Theme Switch Feature

This short blog posts shows you a way of combining bootswatch and gulp together to have an easily useable theme switching support for your web application.
15 October 2014
3 minutes read

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Bootswatch has awesome themes which are built on top of Bootstrap. To integrate those themes to your web application, you have a few options. One of them is to build the css file by combining bootstrap.less file with the less files provided by bootswatch. This is the way I chose to go with. However, what I actually wanted was a little bit more complex:

  • Install bootswatch with bower and have every theme available for me to use.
  • Compile each bootswtch theme to CSS.
  • Concatenate and minify each generated bootstrap file with my other CSS files and have separate single CSS file available for me for each theme.

With this way, switching between themes would be just as easy as changing the filename suffix. I achieved this with gulp and you can find the sample in my GitHub account: gulp-bootswatch-sample. To get the sample up and running, run the following commands in order:

// install bower globally if you don't have it already
npm install bower -g

// install gulp globally if you don't have it already
npm install gulp -g

// navigate to my sample projects root folder and run the following commands
npm install
bower install

// finally run gulp the tasks

Here is how my gulpfile.js file looks like:

var gulp = require('gulp'),
    minifycss = require('gulp-minify-css'),
    concat = require('gulp-concat'),
    less = require('gulp-less'),
    gulpif = require('gulp-if'),
    order = require('gulp-order'),
    gutil = require('gulp-util'),
    rename = require('gulp-rename'),
    foreach = require('gulp-foreach'),
    debug = require('gulp-debug'),
    path =require('path'),
    merge = require('merge-stream'),
    del = require('del');

gulp.task('default', ['clean'], function() {
    gulp.start('fonts', 'styles');

gulp.task('clean', function(cb) {
    del(['assets/css', 'assets/js', 'assets/less', 'assets/img', 'assets/fonts'], cb)

gulp.task('fonts', function() {
    var fileList = [
    return gulp.src(fileList)

gulp.task('styles', function() {
    var baseContent = '@import "bower_components/bootstrap/less/bootstrap.less";@import "bower_components/bootswatch/$theme$/variables.less";@import "bower_components/bootswatch/$theme$/bootswatch.less";@import "bower_components/bootstrap/less/utilities.less";';

    var isBootswatchFile = function(file) {
        var suffix = 'bootswatch.less';
        return file.path.indexOf(suffix, file.path.length - suffix.length) !== -1;
    var isBootstrapFile = function(file) {
        var suffix = 'bootstrap-',
            fileName = path.basename(file.path);
        return fileName.indexOf(suffix) == 0;
    var fileList = [
    return gulp.src(fileList)
        .pipe(gulpif(isBootswatchFile, foreach(function(stream, file) {
            var themeName = path.basename(path.dirname(file.path)),
                content = replaceAll(baseContent, '$theme$', themeName),
                file = string_src('bootstrap-' +  themeName + '.less', content);

            return file;
        .pipe(gulpif(isBootstrapFile, foreach(function(stream, file) {
            var fileName = path.basename(file.path),
                themeName = fileName.substring(fileName.indexOf('-') + 1, fileName.indexOf('.'));
            return merge(stream, gulp.src(['assets/css/font-awesome.css', 'assets/css/main.css']))
                .pipe(concat('style-' + themeName + ".css"))
                .pipe(rename({suffix: '.min'}))

function escapeRegExp(string) {
    return string.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1");

function replaceAll(string, find, replace) {
  return string.replace(new RegExp(escapeRegExp(find), 'g'), replace);

function string_src(filename, string) {
  var src = require('stream').Readable({ objectMode: true })
  src._read = function () {
    this.push(new gutil.File({ cwd: "", base: "", path: filename, contents: new Buffer(string) }))
  return src

End result :)


I wished I had something like this when I started doing this so I hope this was helpful to you somehow. Enjoy!