It's not recognizing "let" keyword, any plans to support it ?

[sohansoni]

It's not recognizing "let" keyword, any plans to support it ?

for e.g. my code is as below
for (let key in item) {

and error is as below:
{ message: 'Unexpected token name «key», expected punc «;»',

[alexlamsl]

uglify-js does not support ES6 - you will need uglify-es for that, which means using the harmony branch of this project:

https://github.com/gruntjs/grunt-contrib-uglify/tree/harmony

[sohansoni]

Thanks, Does uglify-es have backward compatibility for ES5 code as well ?

[alexlamsl]

Yes.

[sohansoni]

How do I get the harmony branch , because when I do npm install grunt-contrib-uglify --save-dev its giving me uglify-js instead of uglify-es ?

[chsyzxcv]

hi sohansoni,
do you find out how to install grunt-contrib-uglify harmony branch ? i am having the same issue as well..

[phoenixdev-kl]

Found it on https://stackoverflow.com/questions/44848273/how-to-integrate-uglify-es-in-grunt

npm install git://github.com/gruntjs/grunt-contrib-uglify.git#harmony --save-dev

If you are behind a firewall like me, please also notice npm/npm#5257. The following worked fine for me:

git config --global url."https://github.com/".insteadOf [email protected]:
git config --global url."https://".insteadOf git://

[liquidvisual]

Thanks for this! Was searching for so long, I thought I was never going to find the answer.

[Kerwood]

When is harmony branch going to be master and published to npm?
Its nice that we have the opportunity to download and use uglify-es manually, but it gives some challenges if your using a automated pipeline..

[samir-mahendra]

I have a weird issue with the "harmony" branch as of 3 days ago. Two different functions are getting uglified into the exact same method name, which causes my code to break.

I found that this older commit from the "harmony" branch gets me back to where I was before:

npm install git://github.com/gruntjs/grunt-contrib-uglify.git#c2ccee1b61a585c5f4fca00da8f79cc1db37048b --save-dev

There is probably a more recent commit, but this worked, so I am using it for now.

If I have time, I'll try to put together a minimum reproducible test case. I'm seeing it in an Angular JS project that uses this dependency: https://github.com/chieffancypants/angular-hotkeys. At first I thought it was due to a change to angular-hotkeys, but then realized it only happened with the uglified code.

[liquidvisual]

I also experienced various errors with everything breaking suddenly, the following fixed it for me:

package.json

"grunt-contrib-uglify-es": "github:gruntjs/grunt-contrib-uglify#harmony",

grunt.js

grunt.loadNpmTasks('grunt-contrib-uglify-es');

.babelrc

{
	sourceType: 'script',
	  presets: [
	    ['env', {modules: false}],
	  ]
}

[induratized]

Use - https://www.npmjs.com/package/terser

npm install terser

It's APIs are compatible with UglifyJS@3 and supports ES6+

[AkashNeil]

I had a similar issue (i.e. not supporting ES6) and fixed it as follows:

npm install grunt-contrib-uglify-es --save-dev

[sitthykun]

Terser is adaptive to ES6+

npm install terser