Error in pipeline build with Gulp

[RandeepSingh]

I am using gulp to compile my assets, however facing the following error during my build about block-scoped declarations. I don't get this error on my local machine and haven't a clue why this is happening

+ gulp build
/opt/atlassian/pipelines/agent/build/node_modules/gulp-sass/index.js:66
 let sassMap;
 ^^^
SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode
 at exports.runInThisContext (vm.js:53:16)
 at Module._compile (module.js:414:25)
 at Object.Module._extensions..js (module.js:442:10)
 at Module.load (module.js:356:32)
 at Function.Module._load (module.js:311:12)
 at Module.require (module.js:366:17)
 at require (module.js:385:17)
 at Object.<anonymous> (/opt/atlassian/pipelines/agent/build/gulpfile.js:4:12)
 at Module._compile (module.js:435:26)
 at Object.Module._extensions..js (module.js:442:10)
 

Here is my build yml file

# This is a sample build configuration for JavaScript.
# Check our guides at https://confluence.atlassian.com/x/14UWN for more examples.
# Only use spaces to indent your .yml configuration.
# -----
# You can specify a custom docker image from Docker Hub as your build environment.
image: atlassian/default-image

pipelines:
  branches:
     master:
       - step:
           caches:
             - node
           script: # Modify the commands below to build your repository.
             - ls -al
             - node -v
             - npm install
             - npm install -g gulp
             - npm install -g gulp-cli
             - npm install -g bower
             - gulp build

And here is my gulpfile.js

 const gulp = require('gulp'),
 sass = require('gulp-sass'),
 plumber = require('gulp-plumber'),
 notify = require('gulp-notify'),
 browserSync = require('browser-sync').create(),
 runSequence = require('run-sequence'),
 del = require('del'),
 purgecss = require('gulp-purgecss'),
 sourcemaps = require('gulp-sourcemaps');

// compile sass files
gulp.task('styles', function () {
 return gulp.src('styles/main.scss')
 .pipe(plumber({ errorHandler: function(err) {
 // show error
 notify.onError({
 title: "Gulp error in " + err.plugin,
 message: err.toString()
 })(err);
 }}))
 .pipe(sourcemaps.init())
 .pipe(sass())
 .pipe(purgecss({
 content: ['**/*.php']
 }))
 .pipe(sourcemaps.write('.'))
 .pipe(gulp.dest('styles/'));
});


// delete the dist folder
gulp.task('clean', function () {
 return del(['dist']);
});

// create dist folder
gulp.task('create-dist-folder', function() {
 return gulp.src([
 'images/*.*',
 'partials/*.*',
 'styles/*.css',
 'work/*.php',
 '.htaccess',
 '*.php',
 '*.ico'], {base: '.'})
 .pipe(gulp.dest('dist'));
});

// clean existing dist folder, rebuild stylesheet and re-create dist folder
gulp.task('build', function (callback) {
 runSequence('clean', 'styles', 'create-dist-folder', callback);
});

[RandeepSingh · Accepted solution]

So after some digging around, I discovered the image I was using contained an older version of node, 

atlassian/default-image

The default image with no version specified so it was using version 1 by default which contained node 4.2.1. The minimum required by my project was 6. So by specifying in the yml file to use version 2 like so meant version 8.94 would be used. 

atlassian/default-image:2

 To see which versions of software are in the image click this link https://hub.docker.com/r/atlassian/default-image/