SyntaxError: Use of const in strict mode

by

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.

More Related Contents:

  1. Why are functions synchronous in Javascript?
  2. Read a file one line at a time in node.js?
  3. Read environment variables in Node.js
  4. nodejs vs node on ubuntu 12.04
  5. Correct way to write loops for promise.
  6. Sequelize model association won’t create a new column
  7. Unable to verify leaf signature
  8. Internal API fetch with getServerSideProps? (Next.js)
  9. Why am I getting weird result using parseInt in node.js? (different result from chrome js console)
  10. Will async/await block a thread node.js
  11. Callback function example
  12. My discord bot code is working but is not responding to my commands [duplicate]
  13. Stubbing a class method with Sinon.js
  14. Download text/csv content as files from server in Angular
  15. Uncaught (in promise) TypeError: Failed to fetch and Cors error
  16. Serial port not working?
  17. When to close MongoDB database connection in Nodejs
  18. Node.js Error: connect ECONNREFUSED
  19. Find out if someone has a role
  20. Writing npm modules in TypeScript
  21. I am getting error in console “You need to enable JavaScript to run this app.” reactjs
  22. How to get data out of a Node.js http get request
  23. How to chain execution of array of functions when every function returns deferred.promise?
  24. How can one get the file path of the caller function in node.js?
  25. Using Express Handlebars and Angular JS
  26. Is there a way to “require” a JS file only once in nodejs?
  27. How to resolve the Syntax error : await is only valid in async function?
  28. Is there a way to read image metadata using node.js
  29. what happens when a Promise never resolves? [duplicate]
  30. ASYNC / AWAIT SyntaxError: await is only valid in async functions and the top level bodies of modules

Leave a Comment