Block-scoped declarations not yet supported outside strict mode

I'm running Laravel 5.4 on my Homestead vagrant box. I've installed all the npm dependencies with npm install command. That didn't produce any errors.

In my webpack.min.js file I have:

const { mix } = require('laravel-mix');

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel application. By default, we are compiling the Sass
 | file for the application as well as bundling up all the JS files.
 |
 */

mix.js([
        'resources/assets/plugins/jquery-1.11.3.min.js',
        'resources/assets/plugins/bootstrap/js/bootstrap.min.js',
        'resources/assets/js/main.js'
    ], 'public/js'
);

mix.combine([
       'resources/assets/plugins/bootstrap/css/bootstrap.min.css',
       'resources/assets/plugins/font-awesome/css/font-awesome.css',
       'resources/assets/css/styles.css'
   ], 'public/css/all.css');

When I want to run npm run production I'm getting the following errors:

> @ production /home/vagrant/projects/nielsvroman
> node node_modules/cross-env/bin/cross-env.js NODE_ENV=production node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js

/home/vagrant/projects/nielsvroman/node_modules/laravel-mix/setup/webpack.config.js:120
        let extractPlugin = new plugins.ExtractTextPlugin(
        ^^^

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:404:25)
    at Object.Module._extensions..js (module.js:432:10)
    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 requireConfig (/home/vagrant/projects/nielsvroman/node_modules/webpack/bin/convert-argv.js:96:18)
    at /home/vagrant/projects/nielsvroman/node_modules/webpack/bin/convert-argv.js:109:17
    at Array.forEach (native)

npm ERR! Linux 3.19.0-25-generic
npm ERR! argv "/usr/bin/nodejs" "/usr/bin/npm" "run" "production"
npm ERR! node v5.0.0
npm ERR! npm  v3.3.6
npm ERR! code ELIFECYCLE
npm ERR! @ production: `node node_modules/cross-env/bin/cross-env.js NODE_ENV=production node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the @ production script 'node node_modules/cross-env/bin/cross-env.js NODE_ENV=production node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js'.
npm ERR! This is most likely a problem with the  package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     node node_modules/cross-env/bin/cross-env.js NODE_ENV=production node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js
npm ERR! You can get their info via:
npm ERR!     npm owner ls
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /home/vagrant/projects/nielsvroman/npm-debug.log

What could be the problem with this?

I had the same problem coused by the old version of nodejs package on Ubuntu. I've just updated to 7.5 and it's working.

curl -sL https://deb.nodesource.com/setup_7.x | sudo -E bash -
sudo apt-get install -y nodejs

Upgrading node package is the solution here. Adding altenative steps to upgrade node package as there is no need to download, install and manage node versions yourself. You can use a module called n to upgrade you node package in Mac/Ubuntu

sudo npm install -g n
sudo n stable

This will install latest stable node package. You can run

node --version

If you are still seeing old version it might be directory issues where new package is installed. I had to create a symlink to make it work-

sudo ln -s  /usr/local/n/versions/node/9.0.0/bin/node  /usr/local/bin/node

I had faced the same problem with one of my test script in NodeJS and i resolved my error by using ECMAScript 5's strict mode.

"use strict";

Added above line at the top of my script and it works well.

Strict mode makes several changes to normal JavaScript semantics:

Eliminates some JavaScript silent errors by changing them to throw errors.
Fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code that's not strict mode.
Prohibits some syntax likely to be defined in future versions of ECMAScript.

This is because you don't have the latest version of NodeJS on your machine. I'm on Ubuntu so if you're on any kind of Linux distro try this.

curl -sL https://deb.nodesource.com/setup_11.x | sudo -E bash -
sudo apt-get install -y nodejs

Your node isn't updated.

remove your node version, download and install the latest version.

in project root run:

npm rebuild

And try again:

npm run production

PS.: If you don't want remove your node version, download the new and run with this.

I was also facing the same issue and I have tried to run these command and now it is working. But before that uninstall the nodejs first

sudo apt-get update

apt-cache policy nodejs

sudo apt install nodejs

I hope your problem will be solved.

来源：https://stackoverflow.com/questions/41960142/block-scoped-declarations-not-yet-supported-outside-strict-mode

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node.js

laravel

laravel-5

Webpack

mix