What is JavaScript

Let’s see what is JavaScript. What are it’s properties. What we can achieve with it and other technologies play well with it.

What is JavaScript

JavaScript was created by Brendon Eich in 1995 to make web page alive. In 1996, Netscape 2 was released with JavaScript 1.0. In 1997 JS became the ECMA standard and since then other browsers started supporting JS.

Initially it was created only as client side language and the program in this language are called scripts and scripts can run directly. They don’t need to be compiled to run. In this aspect it’s very different from java. At that time of creation it was known as LiveScript. But at that time Java was very popular so to use that popularity it was named as JavaScript.

Today JS can run not only in browser but on server also and on any device that has JS engine. Different JS engine has different names like chrome, Opera and edge use V8, SpidarMonkey is used in firefox. SpiderMonkey was created by Brendon Eich himself in 1995 for NetScape2 which is being used in firefox nowadays.

JS engine

Internal working in JS engine is very complicated but if we see the basics it just 3 steps :-

1. The engine reads the script
2. Then it’s converts the script to machine language
3. And then the machine code runs

JavaScript was created mainly to interact with web pages so It doesn’t provide low level access to memory & CPU but with it we can perform almost all operation related to web page. We can :-

1. add new HTML element to a web page, edit existing ones, change styles
2. Perform user events like mouse click, scroll, hover
3. Perform the network call, get data from server, upload data to server
4. user the cache memory, session storage and local storage to store information
5. Show the alert, prompt, pop up to user

What JS can’t do:-

1. To use camera or microphone or any other hardware functionality it requires explicit permission
2. Different window/tabs doesn’t know about each other if there is no agreement between these 2 different pages for safety concern.

Today almost 90% of web contains JS. It’s defacto of modern web. JS simplicity, it’s ability to fully integrate with HTML and CSS and JS engine which is present in almost all the modern browser. Makes it popular and favourite in web development.