SyntaxError Use of const in strict mode

Question

I am trying to login on facebook com with selenium-webdriver   var webdriver   require  selenium-webdriver        By   require  selenium-webdriver   By      until   require  selenium-webdriver   until   var driver   new webdriver Builder        forBrowser  firefox        build     driver get  https   www facebook com login    driver findElement By id  email    sendKeys          driver findElement By id  pass    sendKeys           driver findElement By id  loginbutton    click     driver findElement By linkText  Settings    then function element      console log  Yes  found the element       function error      console log  The element was not found  as expected        driver quit      It is giving error     home shubham node modules selenium-webdriver index js 25 const builder   require    builder          SyntaxError  Use of const in strict mode      at Module  compile  module js 439 25      at Object Module  extensions  js  module js 474 10      at Module load  module js 356 32      at Function Module  load  module js 312 12      at Module require  module js 364 17      at require  module js 380 17      at Object  lt anonymous gt    home shubham Music amazon login test 22 4 16 sel login js 1 79      at Module  compile  module js 456 26      at Object Module  extensions  js  module js 474 10      at Module load  module js 356 32     node --version  v0 10 37  npm  --version1 4 28  protractor --version  Version 3 2 2  selenium-webdriver 2 53 1

User · Answer

cd   npm install -g nave nave use 6 11 1 node app js

User · Answer

Update your node and it will resolve this problem

User · Answer

n stable wouldn t do the trick for me  On the other hand   nvm install stable   That actually got me to last nodejs version  Apparently n stable won t get pass v0 12 14 for me  I really don t know why   Note  nvm is Node Version Manager  you can install it from its github page  Thanks  isaiah for noting that nvm is not a known command

User · Answer

If this is happening in nodejs  it is due to the older version of nodejs  Update node by using   1  Clear NPM s cache   sudo npm cache clean -f   2  Install a little helper called  n   sudo npm install -g n   3  Install latest stable NodeJS version  sudo n stable   Update nodejs instructions taken from  https   stackoverflow com a 19584407 698072

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Usually this error occurs when the version of node against which the code is being executed is older than expected   i e  0 12 or older    if you are using nvm than please ensure that you have the right version of node being used  You can check the compatibility on node green for const under strict mode   I found a similar issue on another post and posted my answer there in detail

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This is probably not the solution for everyone  but it was for me   If you are using NVM  you might not have enabled the right version of node for the code you are running   After you reboot  your default version of node changes back to the system default   Was running into this when working with react-native which had been working fine   Just use nvm to use the right version of node to solve this problem

User · Answer

const is not supported by ECMAScript  So after you specify strict mode  you get syntax error  You need to use var instead of const if you want your code to be compatible with all browsers  I know  not the ideal solution  but it is what it is  There are ways to create read-only properties in JavaScript  see Can Read-Only Properties be Implemented in Pure JavaScript   but I think it might be overkill depending on your scenario   Below is browser compatibility note from MDN   Browser compatibility     The current implementation of const is a Mozilla-specific extension   and is not part of ECMAScript 5  It is supported in Firefox  amp  Chrome    V8   As of Safari 5 1 7 and Opera 12 00  if you define a variable   with const in these browsers  you can still change its value later  It   is not supported in Internet Explorer 6-10  but is included in   Internet Explorer 11  The const keyword currently declares the   constant in the function scope  like variables declared with var        Firefox  at least since version 13  throws a TypeError if you   redeclare a constant  None of the major browsers produce any notices   or errors if you assign another value to a constant  The return value   of such an operation is that of the new value assigned  but the   reassignment is unsuccessful only in Firefox and Chrome  at least   since version 20        const is going to be defined by ECMAScript 6  but with different   semantics  Similar to variables declared with the let statement    constants declared with const will be block-scoped

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Since the time the question was asked  the draft for the const keyword is already a living standard as part of ECMAScript 2015  Also the current version of Node js supports const declarations without the --harmony flag   With the above said you can now run node app js  with app js    use strict   const MB   1024   1024        getting both the syntax sugar and the benefits of strict mode

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The use of const in strict mode is available with the release of Chrome 41  Currently  Chrome 41 Beta is already released and supports it

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Updating NodeJS solves this problem  But  after running sudo npm install -g n you might get following error   npm  relocation error  npm  symbol SSL set cert cb  version libssl so 10 not defined in file libssl so 10 with link time reference   In order to overcome this error  try upgrading openssl using the below command   sudo yum update openssl

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Updating nodejs solved the issue   npm cache clean -f sudo npm install -g n sudo n stable node --version node app js   You have to run the second and third command as root administrator

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One important step after you update your node is to link your node binary to the latest installed node version  sudo ln -sf  usr local n versions node 6 0 0 bin node  usr bin node

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For me it was more simple to solve  just going to the Node web site  get and install the LTS version

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That error means your node s publish is low than the need  carefully to update the node of your computer

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The const and let are part of ECMAScript 2015  a k a  ES6 and Harmony   and was not enabled by default in Node js 0 10 or 0 12  Since Node js 4 x     All shipping  ES2015  features  which V8 considers stable  are turned on by default on Node js and do NOT require any kind of runtime flag      Node js docs has an overview of what ES2015 features are enabled by default  and which who require a runtime flag  So by upgrading to Node js 4 x or newer the error should disappear   To enable some of the ECMAScript 2015 features  including const and let  in Node js 0 10 and 0 12  start your node program with a harmony flag  otherwise you will get a syntax error  For example   node --harmony app js   It all depends on which side your strict js is located  I would recommend using strict mode with const declarations on your server side and start the server with the harmony flag  For the client side  you should use Babel or similar tool to convert ES2015 to ES5  since not all client browsers support the const declarations

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I had a similar issue recently and ended up in this Q amp A  This is not the solution the OP was looking for but may help others with a similar issue   I m using PM2 to run a project and in a given staging server I had a really old version of Node  NPM and PM2  I updated everything  however  I kept keeping the same error      SyntaxError  Use of const in strict mode    I tried to stop and start the application several times  Also tried to update everything again  Nothing worked  Until I noticed a warning when I ran pm2 start       gt  gt  gt  gt  In-memory PM2 is out-of-date  do     gt  gt  gt  gt    pm2 update   In memory PM2 version  0 15 10   Local PM2 version  3 2 9   Gotcha  After running pm2 update  I finally was able to get the application running as expected  No  const in strict mode  errors anymore

[node.js] SyntaxError: Use of const in strict mode?

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