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HTTP stands for Hypertext Transfer Protocol. It is rules for data communication in WWW(Web Wide Web).

Components of a request

In order to make a http request, we need to at least specify:

  1. Request method — what is the type of request we are making.
  2. URI — which resource to apply the request, including…

What is decimal number

Decimal number simple means a number that base on the number 10.

Example: 123 = 100+20+3 = 1*10²+ 1*10¹ + 3*10⁰ = 123

What is a binary number

A number that made by 1s and 0s.

Example: 101 = 1*2² + 0*2¹ + 1*2⁰ = 5

How to convert decimal number to binary number

Divide the decimal number by 2, update the decimal number to quotient until 0 and keep tracking the reminder. The reversed reminder will be the answer.

Example: Given 5 convert to a binary number, the answer is 101.

How to convert binary number to decimal number

To convert a binary number to decimal, simply sum the binary digits together.

Example: Given 100 convert to decimal number, the answer is 4.


What type of click?

There are multiple ways to click an item including Single-click, Double-click, Right-click, Click and drag and Click twice. In this article, I am talking about Single-click.

Browser, Operating System and URL

When you click on a link, the browser and operating system will figure out where you’ve clicked. …


{} and [] in Javascript

{} declare an array.

[] declare an object.

An array is an object so it has all the same capabilities of an object plus a bunch of additional features for managing an ordered, sequential list of numbered indexes starting from 0 and going up to some length.

Array are typically used for:

An ordered list of items that are accessed by numerical index. (lots of features to manage the order of the list or to add or remove things from the list)

JavaScript file extension .Jsx VS .ts VS .js

Plain JavaScript use .js

Anything is not plain JavaScript use .jsx

.ts for TypeScript


  1. Center an image in a web page vertically and horizontally.
  2. Blurring the Image when mouse over.

If we have only have a content division element like so:

<div> </div>

Centering an Image use CSS position and background:

<style>div {
/* Position content division element relative to the nearest positioned ancestor */
/* If the content division element has no positioned ancestors. it uses the document body.*/

position: absolute;

  1. Create 2 html pages and name them page1 and page2.
  2. In page1, create an anchor tag with content “Go to page 2”.
  3. When the mouse clicks on “Go to page 2”, it should pop up a message box.
  4. The message box queries “Are you sure?”. If a user clicks on…

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