JS learnings

currying

var add = function(a){
    return function(b){
        if(b==undefined) return a;
        return add(a+b);
    }
}

es5 inheritence.js

//https://medium.com/@dange.laxmikant/simplified-inheritance-in-js-es5-way-60b4ff19b008

var Person = function(name, age){
	this.name = name;
	this.age = age;
}

Person.prototype.getAge = function(){
	return this.age;
}

let mya= new Person('name', 23);
console.log(mya);
console.log(mya.getAge())

var Emp = function(eid, name, age){
    Person.call(this, name, age);
    this.eid = eid;
}

Emp.prototype = Object.create(Person.prototype);
Emp.prototype.constructor = Emp;
let myb = new Emp(1,'mkl',78);
console.log(myb);
console.log(myb.getAge())
console.log(Emp.prototype.constructor);

hoisting.js

// Basically, when Javascript compiles all of your code, all variable declarations using var are hoisted/lifted to the top of their functional/local scope (if declared inside a function) or to the top of their global scope (if declared outside of a function) regardless of where the actual declaration has been made. This is what we mean by “hoisting”.

// Functions declarations are also hoisted, but these go to the very top, so will sit above all of the variable declarations.

// Enough talk, lets show you some basic examples of code to demonstrate the impact of hoisting.//
//https://medium.com/javascript-in-plain-english/https-medium-com-javascript-in-plain-english-what-is-hoisting-in-javascript-a63c1b2267a1

console.log(myName);  // undefined //no error
var myName = ‘Pradeep’;


///// next file ////
(function() {  //IIFE
   theHero();  //Arrow
   return;
   function theHero() {
       console.log("Arrow");
   }
})();
//----> is changed to 

(function() {
    function theHero() {  //function declaration is hoisted
        console.log("Arrow");
    }
    theHero();            //Arrow
    return;
})();






///////////// other file //////////

//Only a function created with a function declaration is hoisted. The function in return function fn2(){}; is created with a (named) function expression so is not hoisted.

var a = 0;
function b(){
    a= 2;
      function a(){ // . this function named is hoisted above (at start of this function)
        return 1;
    }
    console.log('inside',a) // 2
}
 b();
console.log(a) // 1


// with return ///
var a = 0;
function b(){
    a= 2;
      return function a(){ //not hoisted 
        return 1;
    }
}
 b();
console.log(a) // 2

JS learnings.md

JS learnings

things to note in JS while learning them. putting from my private notes to public gist.

TODO

• hoisting
• Scope of var
• inheritence in es5
• currying
• setTimeout

to study : Named function expressions demystified

scope of var.js

//https://medium.com/@naveenkarippai/scoping-and-hoisting-in-javascript-2c2e82107427
/**
In JavaScript, variables declared (using var keyword) are function-level scoped. The block-level scoping with loops and conditionals ( if,for, while, switch blocks) don’t delimit the scope.
**/
var hero = "Batman";
if(true) {
    var hero = "The Flash";
}
console.log(hero); // "The Flash"


///////////////// other file///////

var hero = "Batman";          //global scope
console.log(hero);            //Batman
(function() {                 //IIFE
   if(true) {
      var hero = "The Flash"; //local scope
      console.log(hero);      //The Flash
   }
})();
console.log(hero);            //Batman