node_js.md

Node.js

require / importing

require = importing what module or file exports

Importing always resolves to one single valid js value

So the imported value it will always represent a single value

• an array
• an object
• a function
• a number
• a string
• undefined
• null

You can require a file path or the name of module example

const value1 = require('./file_name');
const value2 = require('../nested_folder/file_name');
const value3 = require('module_name');

module.exports / exporting

From a javascript file you can export a single value using module.exports =

The common pattern is to export a single object with key-values such as

module.exports = {
  string_value: "1234"
  function_key: function () {},
  object_key: {
    a1: 12341
  },
  array_key: [
    1,
    2,
    3,
    5
  ]
};

So even though we may only export a single value

We can export many values by exporting an object with many key-values

module patterns

It is quite common to group together code by its functionality, responsibility or purpose.

We put all routes in routes folder.

Each file in the routes folder exports a single router.

We put all controllers in a controllers folder.

Each file in the controllers folder exports a single controller.

We put all models in the models folder.

Each file in the models folder exports a single model.

Though each module is only allowed to export a single value such as an object.

We can define many key-values on that exported single object.

For models we can add methods(keys on an object where the value is a function). This will allow us to group together methods together into a model module that is easily consumed from the controllers we define.