Commit d9abae8

<div id="myDiv" style="color: red"><b>Hello World</b></div>

**Q1. Determine whether a year is a leap year or not**

Steps:

1. If the year is evenly divisible by 4, go to step 2. Otherwise, go to step 5.

2. If the year is evenly divisible by 100, go to step 3. Otherwise, go to step 4.

3. If the year is evenly divisible by 400, go to step 4. Otherwise, go to step 5.

4. The year is a leap year (it has 366 days).

5. The year is not a leap year (it has 365 days).

**Q2. Find the length of the string (entered by the user) without using the built-in function.**

Following is the example of output:

**Q3. check whether a number (entered by the user) is a perfect number or not.**

A perfect number, a positive integer that is equal to the sum of its proper divisors. The smallest perfect number is 6, which is the sum of 1, 2, and 3.

Input: 6

Proper divisors of 6 are: 1, 2 and 3

Sum of proper divisors = (1 + 2 + 3) which is equal to 6 (our input)

Hence, 6 is perfect number

**Q4. check whether the number entered by the user is a strong number or not.**

Strong Numbers are the numbers whose sum of factorial of digits is equal to the original number. Given a number, check if it is a Strong Number or not.

Input: 145

Output: Yes

Sum of digit factorials = 1! + 4! + 5!

= 1 + 24 + 120

= 145

**Q5. check whether the number entered by the user is a happy number or not. The user will enter 20 input number and program will check if it is a happy number or not.**

A happy number is starting with any positive integer, replace the number by the sum of the squares of its digits in base-ten, and repeat the process until the number either equals 1 (where it will stay), or it loops endlessly in a cycle that does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers (or sad numbers)

If a number is happy, then all members of its sequence are happy; if a number is unhappy, all members of the sequence are unhappy.

Input: n = 19

Output: 19 is Happy Number,

1^2 + 9^2 = 82

8^2 + 2^2 = 68

6^2 + 8^2 = 100

1^2 + 0^2 + 0^2 = 1

As we reached to 1, 19 is a Happy Number.

**Q6. count all vowels in a sentence (entered by the user).**

Following example shows the output of the program:

Input: Hello C Programming

Output: 5 (vowels)

**Q7. check whether a number entered by the user is magic number or not. The user will enter 1729 input number and program will calculate and check if it is magic number or not and print on the console.**

What is the magic number?

Input: 1729

Sum of digits of the given number.(1 + 7 + 2 + 9 => 19)

The reverse of 19 is 91

The product of digit sum and the reverse of digit sum.(19 X 91 = 1729)

If the product value and the given input are same,

then the given number is a magic number.(19 X 91 <=> 1729)

Output: So, 1729 is a magic number.

let someVar1 = myArray.shift(); // Remove first element and return it

let someVar2 = myArray.pop(); // Remove last element and return it

- DOM Stands for **D**ocument **O**bject **M**odel

- The browser creates a DOM of the page when a webpage is first loaded

- It defines the logical structure of documents and the way a document is accessed and manipulated.

- The HTML DOM model is constructed as a tree of **Objects**:


*Image source: https://www.w3schools.com/js/pic_htmltree.gif*

With the help of DOM, JS can be used to create dynamic HTML.

- Javascript can:

- change all the HTML elements, attributes and CSS styles in the page

- remove existing HTML elements and attributes

- add new HTML elements and attributes

- react to all existing HTML events in the page

- create new HTML events in the page

**Bottom line: The HTML DOM is a standard for how to get, change, add, delete or react to events of the HTML elements.**

<html lang="en">

<meta charset="UTF-8">

<title>Document and Window</title>

<script src="script.js"></script>

<div class="container">

<div id="inner">

<p id="demo">Lorem ipsum dolor sit amet, consectetur adipisicing elit. </p>

<button id="theButton">Hello</button>

</div>

<noscript>JS not supported</noscript>

console.log(document.anchors); // All <a> elements that have a name attribute

console.log(document.body); // get the <body> element

console.log(document.title); // get the <title> element

console.log(document.URL); // get complete URL of the document

<html lang="en">

<meta charset="UTF-8">

<title>DOM Manipulation</title>

<style>

#button {

width: 250px;

height: 250px;

position: absolute;

background-color: #125eff;

}

</style>

<div class="container">

<div id="inner">

<p id="demo" style="border: 1px solid;">Lorem ipsum dolor sit amet, consectetur adipisicing elit. </p>

<input type="text" name="test">

<button class="theButton" onclick="addNewElement()">Hello</button>

</div>

<div class="container2">

<div id="button" onmouseover="oops(this);">

OK

</div>

console.log("document.getElementById('innner')", document.getElementById("inner"));

console.log("document.getElementsByClassName('theButton')", document.getElementsByClassName("theButton"));

console.log("document.getElementsByName('test')", document.getElementsByName("test"));

console.log("document.getElementsByTagName('p')", document.getElementsByTagName("p"));

<script src="script.js"></script>

<noscript>JS not supported</noscript>