global variables in modules using node / express.js

Question

I am trying to avoid using global variables in my server.js file but need variables accessible and writable by various functions. However, I am unsure if scope works the same way as on the client side (since it seems more 'hidden'). I read somewhere that modules have their own scope but if I place variables there and they are accessible in server.js isn't that the same thing as a global scope? For example:

//module.js

var config = [
  {var1: 1},
  {var2: 2},
  {var3: 3}
]

module.exports = {
  config
};

//server.js
const { config } = require("./config.js")

function function1() {
  var a = config[0].var1
  bar b = config[0].var2

  config[0].var3 = a+b // changing var3 value in module

}

Is using modules this way acceptable? If not what would be considered a better practice here?

Thanks

Is using modules this way acceptable? If it works, it's acceptable. Now what you really want to do is unclear... About scope, your answer probably is: Last but not least, let's make this clear — module features are imported into the scope of a single script — they aren't available in the global scope. — Louys Patrice Bessette
– Louys Patrice Bessette, Commented Dec 26, 2019 at 5:02

Muhammad · Accepted Answer · 2019-12-26 07:47:30Z

1

each module has own scope but you can import or export any of variables , functions and etc to other modules and use them in there, like change value of variables but the value will change in module that you imported , not in main

run code below and I think it works as you want it to.

//module.js
var config = [
  {var1: 1},
  {var2: 2},
  {var3: 5} 
]

console.log(config[2].var3) //5

module.exports = config

//server.js
const  config  = require("./app.js")

function function1() {
  var a = config[0].var1
  var b = config[1].var2

  config[2].var3 = a+b // changing var3 value in module
  console.log(config[2].var3) 
}
function1() //3
console.log(config[2].var3)//3


//client.js
const  config  = require("./app.js")
console.log(config[2].var3) //5

answered Dec 26, 2019 at 7:47

Muhammad

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4 Comments

quietplace Over a year ago

Thanks for the info. Just to clarify, the client.js above is still on the server side isn't it? As my understanding is that 'require' is not available on the client side public js modules.

Muhammad Over a year ago

i had a mistake ,actually the name of module.js is app.js in my code in my previous answer to you ,i specified module.js because i wanted ,You understand better,please replace

Muhammad Over a year ago

please replace app.js to module.js or vice versa

Muhammad Over a year ago

and those modules are separate , and their name is desired,actually i created them to show you how modules can deal together

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