gulp-google-closure-compiler-post is a plugin for gulp. It is designed to use the Google Closure Compiler without installing it.
Install this package with NPM and add it to your development dependencies:
npm install --save-dev gulp-google-closure-compiler-post
var closure = require('gulp-google-closure-compiler-post');
gulp.task('javascript', function() {
return gulp.src('./javascript/*.js')
.pipe(concat('all.js'))
.pipe(closure({jsExterns: 'window.ga'}))
.pipe(concat('all.min.js'))
.pipe(gulp.dest('./path/'));
});