How to use global variable in node js

Question

For example I want to use custom logger   logger   require  basic-logger    logger setLevel  info    var customConfig     showMillis  true  showTimestamp  true    var log   new logger customConfig    How to use this logger in other modules instead of console log

User · Answer

May be following is better to avoid the if statement   global logger     global logger   require  my logger

User · Answer

Most people advise against using global variables  If you want the same logger class in different modules you can do this  logger js    module exports   new logger customConfig     foobar js    var logger   require    logger      logger  barfoo      If you do want a global variable you can do   global logger   new logger customConfig

User · Answer

global myNumber    Delclaration of the global variable - undefined global myNumber   5    Global variable initialized to value 5   var myNumberSquared   global myNumber   global myNumber    Using the global variable     Node js is different from client Side JavaScript when it comes to global variables  Just because you use the word var at the top of your Node js script does not mean the variable will be accessible by all objects you require such as your  basic-logger     To make something global just put the word global and a dot in front of the variable s name  So if I want company id to be global I call it global company id  But be careful  global company id and company id are the same thing so don t name global variable the same thing as any other variable in any other script - any other script that will be running on your server or any other place within the same code

User · Answer

I would suggest everytime when using global check if the variable is already define by simply check   if   global logger     global logger   require  my logger        I ve found it to have better performance

User · Answer

you can define it with using global or GLOBAL  nodejs supports both   for e g  global underscore   require  underscore      or  GLOBAL underscore   require  underscore

User · Answer

Global variables can be used in Node when used wisely   Declaration of global variables in Node   a   10  GLOBAL a   10  global a   10    All of the above commands the same actions with different syntaxes   Use global variables when they are not about to be changed  Here an example of something that can happen when using global variables      app js a   10     no var or let or const means global     users js app get   users    req  res  next    gt       res send a      10          permissions js app get   permissions    req  res  next    gt       a   11     notice that there is no previous declaration of a in the permissions js  means we looking for the global instance of a     res send a      11        Explained   Run users route first and receive 10   Then run permissions route and receive 11   Then run again the users route and receive 11 as well instead of 10   Global variables can be overtaken   Now think about using express and assignin res object as global   And you end up with async error become corrupt and server is shuts down   When to use global vars   As I said - when var is not about to be changed   Anyways it s more recommended that you will be using the process env object from the config file

User · Answer

If your app is written in TypeScript  try   global as any  logger            or  Object assign global    logger              However  I will do it only when React Native s   DEV   in testing environment

[node.js] How to use global variable in node.js?

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