The difference between require x and import x

Question

I ve just started working on a small node project that will interface with a MongoDB  However  I cannot seem to get the relevant node modules to import correctly  even though I have installed them correctly via npm   For example  the following code throws an error  telling me that  express has no default export    import express from  express     However  this code works   const express   require  express      So my question is  what is the difference in how the import and variable require methods function  I d like to fix whatever is plaguing my imports on the project  as it seems likely to cause additional problems down the road

User · Answer

Not an answer here and more like a comment, sorry but I can't comment.

In node V10, you can use the flag --experimental-modules to tell Nodejs you want to use import. But your entry script should end with .mjs.

Note this is still an experimental thing and should not be used in production.

// main.mjs
import utils from './utils.js'
utils.print();

// utils.js
module.exports={
    print:function(){console.log('print called')}
}

Ref 1 - Nodejs Doc

Ref 2 - github issue

User · Answer

Let me give an example for Including express module with require  amp  import  -require  var express   require  express      -import  import   as  express from  express     So after using any of the above statement we will have a variable called as  express  with us  Now we can define  app  variable as   var app   express       So we use  require  with  CommonJS  and  import  with  ES6    For more info on  require   amp   import   read through below links   require - Requiring modules in Node js  Everything you need to know  import - An Update on ES6 Modules in Node js

User · Answer

new ES6    import  should be used with  export  key words to share variables arrays objects between js files   export default myObject         in another file  import myObject from    otherFile js     old skool    require  should be used with  module exports    module exports   myObject         in another file  var myObject   require    otherFile js

User · Answer

I will make it simple   Import and Export are ES6 features Next gen JS   Require is old school method of importing code from other files  Major difference is in require  entire JS file is called or imported  Even if you don t need some part of it  var myObject   require    otherFile js      This JS file will be imported fully   Whereas in import you can extract only objects functions variables which are required  import   getDate  from    utils js      Here I am only pulling getDate method from the file instead of importing full file  Another major difference is you can use require anywhere in the program where as import should always be at the top of file

User · Answer

This simple diagram that helps me to understand the difference between require and import      Apart from that   You can t selectively load only the pieces you need with require but with imports  you can selectively load only the pieces you need  That can save memory   Loading is synchronous step by step  for require on the other hand import can be asynchronous without waiting for previous import  so it can perform a little better than require

User · Answer

The major difference between require and import  is that require will automatically scan node modules to find modules  but import  which comes from ES6  won t    Most people use babel to compile import and export  which makes import act the same as require   The future version of Node js might support import itself  actually  the experimental version already does   and judging by Node js  notes  import won t support node modules  it base on ES6  and must specify the path of the module   So I would suggest you not use import with babel  but this feature is not yet confirmed  it might support node modules in the future  who would know     For reference  below is an example of how babel can convert ES6 s import syntax to CommonJS s require syntax   Say the fileapp es6 js contains this import   import format from  date-fns format     This is a directive to import the format function from the node package date-fns     The related package json file could contain something like this    scripts          start    node app js        build-server-file    babel app es6 js --out-file app js        webpack    webpack      The related  babelrc file could be something like this          presets                            env                                  targets                                          node    current                                                      This build-server-file script defined in the package json file is a directive for babel to parse the app es6 js file and output the file app js     After running the build-server-file script  if you open app js and look for the date-fns import  you will see it has been converted into this   var  format   require  date-fns format     var  format2    interopRequireDefault  format     Most of that file is gobbledygook to most humans  however computers understand it     Also for reference  as an example of how a module can be created and imported into your project  if you install date-fns and then open node modules date-fns get year index js you can see it contains   var parse   require     parse index js    function getYear  dirtyDate      var date   parse dirtyDate    var year   date getFullYear     return year    module exports   getYear   Using the babel process above  your app es6 js file could then contain   import getYear from  date-fns get year       Which year is 2 July 2014  var result   getYear new Date 2014  6  2       gt  2014   And babel would convert the imports to   var  get year   require  date-fns get year     var  get year2    interopRequireDefault  get year     And handle all references to the function accordingly

[node.js] The difference between "require(x)" and "import x"

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