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.

&gt; 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).


### gulpfile.js
&lt;!-- language: lang-js --&gt;

    &#39;use strict&#39;;

    const browserify = require(&#39;browserify&#39;);
    const gulp = require(&#39;gulp&#39;);
    const source = require(&#39;vinyl-source-stream&#39;);
    const derequire = require(&#39;gulp-derequire&#39;);
    const buffer = require(&#39;vinyl-buffer&#39;);
    const uglify = require(&#39;gulp-uglify&#39;);
    const sourcemaps = require(&#39;gulp-sourcemaps&#39;);
    const gutil = require(&#39;gulp-util&#39;);
    const path = require(&#39;path&#39;);
    const pkg = require(&#39;./package&#39;);
    const upperCamelCase = require(&#39;uppercamelcase&#39;);

    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(&#39;default&#39;, () =&gt; {
      // set up the browserify instance on a task basis
      var b = browserify({
        entries: INPUT_FILE,
        basedir: SRC_PATH,
        transform: [&#39;babelify&#39;],
        standalone: MODULE_NAME,
        debug: true
      });

      return b.bundle()
        .pipe(source(OUTPUT_FILE))
        .pipe(buffer())
        .pipe(derequire())
        .pipe(sourcemaps.init({loadMaps: true}))
        .pipe(uglify())
        .on(&#39;error&#39;, gutil.log)
        .pipe(sourcemaps.write(&#39;.&#39;))
        .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&#39;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?


## Update

I have temporarily (or permanently) replaced UglifyJS with [Butternut](https://github.com/Rich-Harris/butternut) and seem to work.

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UglifyJS throws unexpected token: keyword (const) with node_modules