console.warn("Warning on the console");
console.error("Used to write error on the console");
console.clear("Used to clear console");

var a = 12;
var  b = 13;
console.log(a + b);
document.write(a + b);

String data types
var str1 = "This sia awanish kumar";
var str2 = "This is Manish";

Number Data Types
var a = 12; 
var b = 23;

Object

var marks = {
    Awanish : 12,
    Manish: 23,
    Sunish : 45
};

console.log(marks);


Booleans
var a= true;
var b = false;

console.log(a, b);

if we just declare a variable and donot initialize it then it is by default undefined
var und = undefined;
console.log(und); 

var n = null

Null and undefinedare diffrent.


At a very high level data type can be of two type 
1.Fundamental data type - number, null, boolean, undefined, symbol, string
2. Reference data type - arrays, objects

Arrays
var arr = [1,2,"Awanish",4,5,6,7,8,9];
console.log(arr);
console.log(arr[0]);
console.log(arr[2]);

var a = 1200;
var b = 120;
console.log(a + b);
console.log(a - b);
console.log(a * b);
console.log(a / b);
console.log(a == b);
console.log(a != b);
console.log(a >= b);
console.log(a <= b);
console.log(a > b);
console.log(a < b);
console.log(a % b);

console.log(true && true);
console.log(true && false);
console.log(false && false);
console.log(!true);
console.log(true || false);

DRY - DONOT REPEAT YOURSELF

function avg(a, b){
    return (a + b)/2;
}
c1 = avg(12,25);
c2 = avg(12, 12);
console.log(c1, c2);

var age = 13;
if(age>12){
    console.log("you are not a kid");
}else{
    console.log("You are a kid");
}

var  num = 12;

if(num > 0){
    console.log("The number is positive");
}else if(num < 0){
    console.log("Number is less than zero");
}else{
    console.log("Number is equla to zero");
}

var arr = [1,2.3,4,5,5,7,4,74,"Awnaish", "Awanish",564];
for(var i = 0; i < arr.length; i++){

    console.log(arr[i]);
}

arr.forEach(function(element){
    console.log(element);
})

var i = 0;
We should use let instead of var
const a = 0;  // cannot be updated.
while(i<arr.length){
    console.log(arr[i]);
    i += 1;
}

do{
    console.log(arr[i]);
    i++;
}while(i < arr.length);


var arr = [1,2.3,4,5,5,7,4,74,"Awnaish", "Awanish",564];
let i = 0;
// console.log(arr.pop);

arr.pop();  // pop from the bottom
console.log(arr) 
arr.push(null)     // push at the bottom
arr.push(487485);
arr.push(true)
console.log(arr)

arr.shift();  // Shift one element from the left or from the top

console.log(arr);

arr.unshift("Awanish_Kumar Singh");  // pushes at the left of array or top of array

console.log(arr);

arr.toString();

console.log(arr);

var arr = [1,2,3,4,3,2000,1000];
console.log(arr)
arr.sort();
console.log(arr)  // sorts the elements according to the alphabets......

date = new Date();
console.log(date)
console.log(date.getTime())
console.log(date.getFullYear());
console.log(date.getDay());
console.log(date.getMinutes())
console.log(date.getHours(0))

console.log(document);
console.log(document.location);

document.getElementById("button").click();
document.getElementById("button").style.border = "2px solid blue";

var element = document.getElementById("button")
console.log(element)

var element = document.getElementsByClassName("container")
console.log(element);
element[0].style.background ="yellow"
element[0].classList.add("awanish");  //adding class to a element.
element.classList.remove("awanish")   // removing a class from a element.

el = document.getElementsByTagName("div")
console.log(el)

el = document.getElementById("button");
console.log(el)
console.log(el.innerHtml);
console.log(el.innerText)

el = document.getElementsByTagName("div")
createdElement = document.createElement("p");
createdElement.innerText  = "This is Awanish kumar singh"
el[0].appendChild(createdElement);
//We can even replace elements
createdElement2  = document.createElement('b')
createdElement.innerText = 'This is bold'
el[0].appendChild(createdElement2,createdElement);
el[0].removeChild(createdElement2);
el[0].removeChild(createdElement);

console.log(document.location);
console.log(document.URL);
console.log(document.scripts);
console.log(document.title)

document.domain, document.forms etc.......

el = document.querySelector('.container')
console.log(el)


el = document.querySelectorAll('.container');
console.log(el[0]);

we can even select the event also

using html onclick method

function clicked(){
    console.log('This is the boy I was talking about');
}

window.onload = function(){
    console.log('The doment was loaded');
}

firstContainer.addEventListener('click', function(){

    console.log('This is awanish')
})

firstContainer.addEventListener('mouseover', function(){

    console.log('Mouse is hovering'); 
})

firstContainer.addEventListener('mouseout', function(){

    console.log('Mouse is out of the station')
})

firstContainer.addEventListener('mouseout', function(){

    console.log('Mouse is out of the station')
})


firstContainer.addEventListener('mouseup', function(){

    console.log('Mouse is up when clicked')
})

firstContainer.addEventListener('mousedown', function(){

    console.log('Mouse is down when clicked')
})


Arrow function
function sum(a , b){
    return a + b;
}

sum = (a,b)=>{
    return a + b;
}

console.log(sum(45,60));

logKaro = ()=>{
    alert('HEllo Bachu')
}

setTimeout(logKaro, 3000); It runs the following code only one time.


runs the following code multiple time
setInterval(() => {
  alert('Hello bachhu');  
}, 2000);

or
setInterval(logKaro, 2000);

obj = {name:"Awanish", length:7};
jso = JSON.stringify(obj);
console.log(jso)
console.log(typeof jso);
parsed = JSON.parse(`{"name":"Awanish","length":7}`);
console.log(parsed)
console.log(typeof parsed)


Use of back ticks  ---  ``
var a = 10;
console.log("This is my ", a);
using backticks 
console.log(`This is my ${a}`);