How to avoid access mutable variable from closure

by

You need to create a scope to correctly capture tmp_id using a self-executing function. That’s because the entire for loop is one scope, meaning each time through, you’re capturing the same variable. So the callback will end up with the wrong ids, because temp_id‘s value will get changed before the callback is called.

I’d ignore (or shut off) the warning, though, which seems to be complaining that because temp_id is mutable, you might reassign it. That’s sort of silly. If you really want to fix it, try using the const keyword instead of var.

for(var id=0; id < message.receiver.length; id++){
   (function(){
       const tmp_id = id;
       zlib.gzip(JSON.stringify(message.json), function(err, buffer){
                        ...
           pushStatusPool[message.receiver[tmp_id]] = null; // fix memory leak
           delete pushStatusPool[message.receiver[tmp_id]];
           ...
       });
   })();
}

More Related Contents:

  1. Static variables in JavaScript
  2. module.exports vs exports in Node.js
  3. Mocha / Chai expect.to.throw not catching thrown errors
  4. Callback after all asynchronous forEach callbacks are completed
  5. Why does a while loop block the event loop?
  6. What underlies this JavaScript idiom: var self = this?
  7. How can I share code between Node.js and the browser?
  8. Best way to call an asynchronous function within map?
  9. How can i export socket.io into other modules in nodejs?
  10. Rest with Express.js nested router
  11. What is NODE_ENV and how to use it in Express?
  12. setTimeout() inside JavaScript Class using “this”
  13. Module not found: Error: Can’t resolve ‘crypto’
  14. Send a message with Discord.js
  15. Creating Rooms in Socket.io
  16. How do I upload a base64 encoded image (string) directly to a Google Cloud Storage bucket using Node.js?
  17. Eslint does not allow static class properties
  18. node.js – Code Protection?
  19. Environment detection: node.js or browser
  20. res.sendfile in Node Express with passing data along
  21. In the `import` syntax of ES6, how is a module evaluated exactly?
  22. Curly brackets (braces) in Node.js ‘require’ statement
  23. Checking if a message was sent from a DM not working
  24. Spawn and kill a process in node.js
  25. Can the browser turned headless mid-execution when it was started normally, or vice-versa?
  26. Closures in a for loop and lexical environment
  27. Socket.io – Manual reconnect after client-side disconnect
  28. Group by Date with Local Time Zone in MongoDB
  29. JavaScript EventSource SSE not firing in browser
  30. Node JS fs module inside browser

Leave a Comment