CODEWITHSUNDEEP
javascriptnode.js
userMod2
userMod2

Reputation: 8960

Basic JS - Declaring require var and using inside class

I have a JS class declared as such:

class Useful {
  someFunction(index) {
    //Does something with index
}

However I'm unsure what the best practice is to declare require variables such as var fs = require('fs') and how to use it - namely:

Thanks.

UPDATE - following comments - is this correct

const fs = require('fs')

    class Useful {
      someFunction(index) {
        //Does something with index
        fs.writeFile(......)
    }

Upvotes: 0

Views: 69

Answers (2)

Jonas Wilms
Jonas Wilms

Reputation: 138427

A

class Useful {
  someFunction(index) {
     const fs = require("fs");
  }
}

B

const fs = require("fs");
class Useful {
  someFunction(index) {

  }
}

Theres an important difference between these two: In A, fs will be loaded every time someFunction is called. This is bad for performance and has no real advantage. So use B.

Upvotes: 0

kunal pareek
kunal pareek

Reputation: 1283

1) All module require declarations should ideally be at the top of the file.

const useful = require('useful')

class foo ....

2) 'this' refers to the class itself and so you need to explicitly attach the module you just imported inside the class constructor as a class property if you need it like that

class Useful (importedModule) {
    constructor(importedModule) { // constructor syntactic sugar
        this.module = importedModule;
    }

3) With es6 you can also import your modules with 

import somethingUseful from 'module_or_./filePath_where_something_useful_is_kept'

4) with es6 let and const are much better alternatives to var.

Upvotes: 1

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