A small project I started make use a node module (installed via npm) that declares const
variables. Running and testing this project is well, but browserify fails when UglifyJS is executed.
Unexpected token: keyword (const)
Here is a generic Gulp file that I have successfully been using for a few other past projects without this issue (i.e. without that particular node module).
'use strict';
const browserify = require('browserify');
const gulp = require('gulp');
const source = require('vinyl-source-stream');
const derequire = require('gulp-derequire');
const buffer = require('vinyl-buffer');
const uglify = require('gulp-uglify');
const sourcemaps = require('gulp-sourcemaps');
const gutil = require('gulp-util');
const path = require('path');
const pkg = require('./package');
const upperCamelCase = require('uppercamelcase');
const SRC_PATH = path.dirname(pkg.main);
const DIST_PATH = path.dirname(pkg.browser);
const INPUT_FILE = path.basename(pkg.main);
const OUTPUT_FILE = path.basename(pkg.browser);
const MODULE_NAME = upperCamelCase(pkg.name);
gulp.task('default', () => {
// set up the browserify instance on a task basis
var b = browserify({
entries: INPUT_FILE,
basedir: SRC_PATH,
transform: ['babelify'],
standalone: MODULE_NAME,
debug: true
});
return b.bundle()
.pipe(source(OUTPUT_FILE))
.pipe(buffer())
.pipe(derequire())
.pipe(sourcemaps.init({loadMaps: true}))
.pipe(uglify())
.on('error', gutil.log)
.pipe(sourcemaps.write('.'))
.pipe(gulp.dest(DIST_PATH))
;
});
I have tried fixing this by replace all const
to var
in that npm-installed module, and everything is fine. So I do not understand the failure.
What's wrong with const
? Unless someone uses IE10, all major browsers support this syntax.
Is there a way to fix this without requiring a change to that node module?
I have temporarily (or permanently) replaced UglifyJS with Butternut and seem to work.
As ChrisR mentionned, UglifyJS does not support ES6 at all.
You need to use terser-webpack-plugin for ES6 (webpack@5 will use this plugin for uglification)
npm install terser-webpack-plugin --save-dev
Then define in your plugins
array
const TerserPlugin = require('terser-webpack-plugin')
new TerserPlugin({
parallel: true,
terserOptions: {
ecma: 6,
},
}),