class - how to uglify javascript classes? - Stack Overflow

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I'm writing basic javascript using the classes syntax and trying to uglify it with gulp, but getting this error:

events.js:72
throw er; // Unhandled 'error' event

I simply used the example code from mozilla's website:

class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }
}

And nothing special about my gulp file - works perfectly for any non-class js:

// Include gulp
var gulp = require('gulp');

// Include Our Plugins
var jshint = require('gulp-jshint');
var concat = require('gulp-concat');
var uglify = require('gulp-uglify');
var rename = require('gulp-rename');

// Lint Task
gulp.task('lint', function() {
    return gulp.src('js/*.js')
        .pipe(jshint())
        .pipe(jshint.reporter('default'));
});

// Concatenate & Minify JS
gulp.task('scripts', function() {
    return gulp.src('js/*.js')
        .pipe(concat('all.js'))
        .pipe(gulp.dest('dist/js'))
        .pipe(rename('all.min.js'))
        .pipe(uglify())
        .pipe(gulp.dest('dist/js'));
});

// Watch Files For Changes
gulp.task('watch', function() {
    gulp.watch('js/*.js', ['lint', 'scripts']);
    gulp.watch('scss/*.scss', ['sass']);
});

// Default Task
gulp.task('default', ['lint', 'scripts', 'watch']);

I'm writing basic javascript using the classes syntax and trying to uglify it with gulp, but getting this error:

events.js:72
throw er; // Unhandled 'error' event

I simply used the example code from mozilla's website:

class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }
}

And nothing special about my gulp file - works perfectly for any non-class js:

// Include gulp
var gulp = require('gulp');

// Include Our Plugins
var jshint = require('gulp-jshint');
var concat = require('gulp-concat');
var uglify = require('gulp-uglify');
var rename = require('gulp-rename');

// Lint Task
gulp.task('lint', function() {
    return gulp.src('js/*.js')
        .pipe(jshint())
        .pipe(jshint.reporter('default'));
});

// Concatenate & Minify JS
gulp.task('scripts', function() {
    return gulp.src('js/*.js')
        .pipe(concat('all.js'))
        .pipe(gulp.dest('dist/js'))
        .pipe(rename('all.min.js'))
        .pipe(uglify())
        .pipe(gulp.dest('dist/js'));
});

// Watch Files For Changes
gulp.task('watch', function() {
    gulp.watch('js/*.js', ['lint', 'scripts']);
    gulp.watch('scss/*.scss', ['sass']);
});

// Default Task
gulp.task('default', ['lint', 'scripts', 'watch']);

• javascript
• class
• gulp-uglify

Share Improve this question Follow asked Apr 7, 2016 at 16:29 Jeff PuckettJeff Puckett 41.1k1919 gold badges124124 silver badges174174 bronze badges 6

• 6 Classes are only available in ECMAScript6; Are you sure your environment supports ES6? – Brian Driscoll Commented Apr 7, 2016 at 16:32
• to which environment are you referring? the code works as expected in my browser, and it passes the lint. – Jeff Puckett Commented Apr 7, 2016 at 16:38
• The env where you are running gulp – Brian Driscoll Commented Apr 7, 2016 at 16:39
• How would I verify this? I'm running ubuntu 14.04.3, nodejs v0.10.44, npm 3.8.5, gulp CLI 1.2.1 local 3.9.1, gulp-uglify 1.5.3 – Jeff Puckett Commented Apr 7, 2016 at 16:47
• 1 Jeff, it would be your node.js installation. See here: kangax.github.io/pat-table/es6 – Brian Driscoll Commented Apr 7, 2016 at 17:37

 |  Show 1 more ment

1 Answer 1

Sorted by: Reset to default 6

At the time, I resolved this with a workaround by transpiling to ECMA 5 with Babel.

Later I discovered it was not a problem with my Node environment as the ments led me to believe, but in fact it was because the default uglify branch used in gulp-uglify doesn't support ECMA 6 yet.

The correct solution was to instead use the harmony branch of UglifyJS2 or to use the npm wrapper uglify-js-harmony.

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