Javascript: Syntax ( key concepts or 1 new things )

PHOTO EMBED

Sun Jun 13 2021 15:37:36 GMT+0000 (Coordinated Universal Time)

Saved by @jpannu #angular #typescript 

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                                //Number


Number.isNaN(24);
// False.

let number1 = -Infinity;
let number2 = Infinity;  
--------------------
                                   //String


String(77).padStart(6,0);
// 000077


let str = 'Jaskaran Singh Pannu';
str.repeat(10)

console.log("Karan- ".repeat(4));
//Karan- Karan- Karan- Karan-
-------------------
-------------------

-------------------
                                   //Object
  
  
let {name , age} = {name: "Faraji", age: 23};
console.log(name , age);
// → Faraji , 23


let obj = { name  : 'karan' };
consol.log( 'name' in obj);
//true;

     // Prototype ( Just to check if the certain properties are there.
Object.prototype.addNewMethod = function(){ return "Yeah"};
console.log('addNewMethod' in Object);
//true;
console.log('toString' in Object);
//true;

 //hasOwnProperty  ( It will just show the 'obj's properties ( code written ) , Not of it's parent ( Object).
let obj = { name : 'karan' };
obj.hasOwnProperty("name");
//true;
obj.hasOwnProperty('toString');
//False;

 //Get  // Set //Statics.
let obj = {
  //keyword 'get'
  get powerOne(){ return "Power 1" },
  powerTwo : function(){
    return "Power2, Old School."
  }
};
obj.powerOne;
// OR. (The Only difference is, If we are using keyword "get", We don't have to use "()" while calling any function.
obj.powerTwo();
------------------------
                                //Classes
class basics{
  constructor( name  ){
     this.name = name;
  }
  skillOne(skill){
    return this.name + " is " + skill
  }
}

class ChildOne extends basics{
  constructor( name , age , country ){
    super( name )
    this.age = age;
    this.country = country;
  }
  skillTwo(){
    return " Skill Two here... "
  }
}
----------------------
//instanceof
let arr = {};
console.log(arr instanceof Object)
// true.
let arr2 = []
console.log(arr2 instaceof Object);
// true ( Object is main base for all the non-primitives data types ( functions / arrays ).
------------------------
//Object.freeze
let object = Object.freeze({value: 5});
object.value = 10;
console.log(object.value);
// → 5
-----------------------
                               //HOF
  //Data.
const companies = [
  {name: "Company One", category: "Finance", start: 1981, end: 2005},
  {name: "Company Two", category: "Retail", start: 1992, end: 2008},
  {name: "Company Three", category: "Auto", start: 1999, end: 2007},
  {name: "Company Four", category: "Retail", start: 1989, end: 2010},
  {name: "Company Five", category: "Technology", start: 2009, end: 2014},
  {name: "Company Six", category: "Finance", start: 1987, end: 2010},
  {name: "Company Seven", category: "Auto", start: 1986, end: 1996},
  {name: "Company Eight", category: "Technology", start: 2011, end: 2016},
  {name: "Company Nine", category: "Retail", start: 1981, end: 1989}
];
const ages = [  10, 0,10, 40, 50 , 88, 9 , 20 ,89, 100 ,6];


//Sort
let sort = ages.sort((a , b ) => a - b );
sort = companies.sort( (a , b ) =>  a.start -b.start    )

//Reduce , Suming the Arrays.
let totatAges = ages.reduce(( total, item )=> total + item, 0 );
let totalYears = companies.reduce(( total , item ) => total + (item.end - item.start)
,0)

let out = nums.reduce(( firstItem , singleItem ) => {
 let max = firstItem > singleItem ? firstItem : singleItem;
 return max; 
})


// There is another method called => "Find" 

                        /* "Every" */ ( it return boolean value ) 
//It will test whether all elements in the array pass the provided function.
let output = students.every((item)=>{
  return item.grade >= 100;
})

                       /* "SOME"  */  ( it return boolean value )
//Similar to every, but returns true if ANY of the array elements pass the test function
let output = students.some((item)=>{
  return item.grade >= 100;
})



//Combined
let combined = ages
                   .sort((a,b) => a-b)
                   .filter( item => item <= 10 )
                   .map( item => item * 1 ) 
                   .reduce( (total,item)=> total + item ,0 );

//Destructing 
//Objects example
let  {name, age, ...evrythingElse} = {  name : 'Jaskaran',  age : 34, country : "U.S", cool : true }
console.log(name); //Jaskaran
console.log(age); //34
console.log(evrythingElse); // { country:'U.S', cool: true }

//Array Example
let arr = ["Jaskaran","Singh","Pannu"];
let  [firstName, ...everythingElse ]  = arr;
console.log(everythingElse); // ['Singh', 'Pannu']


//Param Destructing
let fullName = ({fN, lN }) =>{ return fN + " " + lN }

let objName = {
  fN : "Karan",
  lN :"Singh"
}

fullName(objName);



/* Async */


//1 way.
fetch("https://icanhazdadjoke.com/slack").then((res)=>{
        res.json().then((data)=>{
        console.log(data)
    })
});

//2nd Way
let link = "https://icanhazdadjoke.com/slack";
let xhr = new XMLHttpRequest();

xhr.open('GET',link, true);
xhr.send();

xhr.onreadystatechange = function(){
if(xhr.readyState == 4){
    console.log(xhr.responseText);
 }
}
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