Basic Javascript

// multiple loop
for(i = 0, j = 10; i<=10, j>=0; i++, j--){
    console.log(i, j);
}


// factorial 1-10
var factorial = 1;
for(n = 1; n <= 10; n++){
    factorial *= n;
    console.log("factorial of ", n , "is ", factorial);
}


// Number series 

// s1 = 2 4 6 8 10 12 14 ...
var series = "";
var n;
for(i = 0; i < 10; i++){
    n = i*2;
    series = series + n + " "; 
}
console.log("Series One = " + series);



// s2 = 1 4 7 10 13 16 ...
var series = "";
var n = 1;
for(i = 0; i < 10; i++){
    n = n + 3;
    series = series + n + " "; 
}
console.log("Series Two = " + series);



// s3 = 0 3 8 15 24 35 45 ...
var series = "";
var n;
for(i = 1; i < 10; i++){
    n = i*i-1;
    series = series + n + " "; 
}
console.log("Series Three = " + series);



// s4 = 1 4 3 8 5 12 7 16 ....
var series = "";
for(i = 1; i < 10; i++){
    n = i;
    if(n%2 == 0){
        n = n*2;
    }
    series = series + n + " ";
}
console.log("Series Four = " + series);



// s5 = 0 1 1 2 3 5 8 13 ... fibonacci
var series = "0 1 ";
var x = 0;
var y = 1;
for(i = 0; i < 10; i++){
    n = x+y;
    x = y;
    y = n; 

    series = series + n + " ";
}
console.log("Series Four = " + series);



// divisors
var n = 148;
var range = Math.ceil(Math.sqrt(n));
var divisors = "";

for(i=0; i<=range; i++){
    if(n%i == 0){
        if(i == n/i){
            divisors += i + " ";
        }else{
            divisors += i + " " + (n/i) + " ";
        }    
    }
}
console.log(divisors);



// Calendar
var monthName = "May";
var days = 31;
var startingday = 2;

console.log("Calendar of ",monthName,"\n");
console.log("Sun   Mon   Tue   Wed   Thu   Fri   Sat");

for(var i=0; i<5; i++){
    var dayRow = "";
    for(var j=1; j<=7; j++){
        var currentDay = 7*i + j - startingday;
        
        if(currentDay>days){
            break;
        }else if(currentDay<1){
            currentDay = " ";
        }

        if(currentDay>9){
            dayRow += currentDay + "    ";
        }else{
            dayRow += currentDay + "     ";
        } 

    }
    console.log(dayRow);
}



//Array
var fruits = ["Apple","Banana","Orange","Date","Grape"];
console.log(fruits[0]);


// last element
var lastIndex = fruits.length-1;
console.log(fruits[lastIndex]);


// slice, splice
var list = [
    "sun", //0 = -7
    "mon", //1 = -6
    "tue", //2 = -5
    "wed", //3 = -4
    "thu", //4 = -3
    "fri", //5 = -2
    "sat"  //6 = -1
];

var chunk = list.slice(1, 4);
console.log(list,chunk);
console.log("\n");

var chunk = list.splice(1, 4);
console.log(list,chunk);



// deep copy
var list = [
    "sun", //0 = -7
    "mon", //1 = -6
    "tue", //2 = -5
    "wed", //3 = -4
    "thu", //4 = -3
    "fri", //5 = -2
    "sat"  //6 = -1
];

var list2 = list;
list2[2] = "No Day";
console.log(list2, list);



// shallow copy
var v1 = 1;
var v2 = v1;
v2 = 2;
console.log(v1,v2);


// array merge
var list1 = ["sun","mon","tue"];
var list2 = ["wed","thu","Fri"];

var list = list1.concat(list2);
console.log(list);

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DOM and BOM

|| BOM (Browser Object Model)
	The BOM (Browser Object Model) consists of the objects navigator, history, screen, location
		navigator	-> The navigator object contains information about the browser.
		history		-> The history object contains the URLs 
		screen		-> The screen object contains information about the visitor's screen.
		location	-> The location object contains information about the current URL.
		
|| Dom 
	what is dom?
	The DOM is an API (application programming interface). 
	যেটি  একটি ডকুমেন্টের কাঠামো, ধরণ ও কনটেন্টকে পরিবর্তন করে।
	
	when is creates?
	When a web page is loaded, the browser creates a Document Object Model of the page.
	
	how you can use the document object ?
		-> Finding HTML Elements
			document.getElementById(id)
			
		-> Changing HTML Elements
			element.innerHTML =  new html content
		
		-> Adding and Deleting Elements
			document.createElement(element)
			document.removeChild(element)