JS Fundamentals Review + NodeJS Modules Review / Examples.

00-js-foundations.md

JS Foundations

Topics:

• Scopes in JS
• Context (aka this) in JS
• Callbacks Review
• NodeJS Modules
• NodeJS Automated Testing w. Mocha - time permits

Setup:

1. Create the following skeleton of files:

./01-scope.js
./02-context.js
./03-callbacks.js
./04-modules.js
./lib
./lib/util.js
./README.md

2. Create a package.json file by running npm init -y in your terminal

3. Remember to include use strict; at the top of all of your files

Strict mode helps out in a couple ways:

It catches some common coding bloopers, throwing exceptions. It prevents, or throws errors, when relatively "unsafe" actions are taken (such as gaining access to the global object). It disables features that are confusing or poorly thought out.

Read Full Article

01-scope.js

// global scope start
'use strict';

var name = 'Faisal';

var printSomething = function(data){
  // local scope 1 start
  var delay = function(){
    // local scope 2 start
    var data_inside_delay = 5;
    console.log('...')
    console.log('...')
    console.log(data);
    // local scope 2 end
  }

  console.log(data_inside_delay);
  delay();
  // local scope 1 end
}

printSomething(name);
// global scope end

02-context.js

'use strict';

const greeting = function(){
    console.log("Hi my name is " + this.name);
}
const people = [
  {
    name: 'Faisal',
    age: 23,
    greeting: greeting
  }, {
    name: 'ABC',
    age: 99,
    greeting: greeting
  }
]

people[0].greeting();

03-callbacks.js

'use strict';

const people = [
  {
    name: 'Faisal',
    age: 23
  }, {
    name: 'Jane',
    age: 45
  }, {
    name: 'ABC',
    age: 99
  }
]

const filter = function(data, _cb){
  const output = [];
  // for each element in data
  data.forEach(function(elm){
    // check if this element is to be included in the output
    if(_cb(elm)){
      output.push(elm);
    }
  });
  // once all elements have been checked
  return output;
}

const peopleFilterFunc = function(person){
  return person.name.length <= 4;
}

const under_50 = filter(people, peopleFilterFunc);
console.log(under_50);

04-modules.js

package.json

{
  "name": "js-foundations",
  "version": "1.0.0",
  "description": "",
  "main": "01-scope.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
}

util.js