Javascript

JavaScript: Getting started

JavaScript is used to create client-side dynamic pages. JavaScript is an object-based scripting language which is lightweight and cross-platform.

Javascript First Program:

console.log("Welcome to Stately World");

Table of Contents

Tools For JavaScript Programming

There are some tools including frameworks, debuggers, text editors, etc. that will help you code efficiently using JavaScript.

Text Editors

You can use  Sublime Text, Notpad++, Visual Code, etc as a text editor.

Browser

You can use any browser for Javascript program. I am listing some browser name below.

  1. Google Chrome
  2. Firefox
  3. Microsoft Edge

Display output in JavaScript

JavaScript can “display” data in different ways:

  1. console.log('Hello World');
  2. document.write()
  3. window.alert()

Getting an element in Javascript:

* getElementByID()
* getElementsByClassName()
* getElementsByTagName()
* querySelector() + querySelectorAll()

Creating things in the documents

* createElement()
* createAttribute()

Example: Multidimensional Array

var activities = [
		    ['Work', 9],
		    ['Eat', 2],
		    ['Commute', 2],
		    ['Play Game', 2],
		    ['Sleep', 7]
		];

		activities.push(['Study',2]);							

for (var i = 0; i < activities.length; i++)
{

	console.log(i);

    var percentage = ((activities[i][1] / 24) * 100).toFixed();
    
    activities[i][2] = percentage + '%';
}

console.log(activities.join('\n'));


// loop the outer array
for (var i = 0; i < activities.length; i++) 
{
    // get the size of the inner array
    var innerArrayLength = activities[i].length;
    // loop the inner array
    for (var j = 0; j < innerArrayLength; j++)
    {
        console.log('[' + i + ',' + j + '] = ' + activities[i][j]);
    }
}

Object.keys, values, entries

For plain objects, the following methods are available:

Object.keys(obj) – returns an array of keys.
Object.values(obj) – returns an array of values.
Object.entries(obj) – returns an array of [key, value] pairs.