Who & why JavaScript was created
In 10 days, by Brendan Eich ,initially created to “make web pages alive !"
Nature of JavaScript
Its Dynamic
supports two programming language paradigms: functional & object-oriented programming
It’s deployed as source code
Its Asynchronus
Standardizing JavaScript
Language described by these standards is called ECMAScript, not JavaScript
ECMAScript 1
First version of the standard.
ECMAScript 5
Strict Mode
This strict context prevents certain actions from being taken and throws more exceptions
"use strict";ECMAScript 6
let,classes,=> ,... and Much More!
JavaScript can change HTML content.
JavaScript Can Change HTML Attribute Values
JavaScript can "display" data in different ways:
Change HTML element content, element.innerHTML.
Writing output , document.write().
Writing into the browser console, console.log().JavaScript Hoisting
JavaScript Declarations are Hoisted
a variable can be used before it has been declared.
x = 5; // Assign 5 to x elem = document.getElementById("demo"); // Find an element elem.innerHTML = x; // Display x in the element var x; // Declare xSimilarly Function declrations are Hoisted
JavaScript only hoists declarations, not initializations.
JavaScript Variables
var x = 6;
const y= 6; ES6
let x = 6; ES6
Note - JavaScript is Case Sensitive
JavaScript Data-Types
Number var length = 16;
String var lastName = "Johnson";
Object var x = {name:"J", id:25};
Undefined var undef = undefined;
Null var nul = null;
Array var arr = ["A",'J',123,null];
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JavaScript Objects
used to store various keyed collections and more complex entities.
All JavaScript values, except primitives, are objects.
Object Literals
var emptyObject = {};Object Constructor
var person = new Object(); JavaScript Popup Boxes
Attention!
Understanding 'this' in JavaScript
Checkout my Github- Checkout String
Strings in JavaScript
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Arrays in JavaScript
Date JavaScript
JavaScript Scheduling
setTimeout ( expression, timeout );Call function after specific miliseconds
Change content after 1 sec
JavaScript Scheduling
setInterval ( expression, timeout );keeps triggering expression regularly
Change content afte every 500 ms
IIEF JavaScript
IIFE (Immediately Invoked Function Expression) is a JavaScript function that runs as soon as it is defined.
(function () {// logic here }) ();JavaScript Closures
A closure is the combination of a function and the lexical environment within which that function was declared.
function User(name){ var displayName = function(greeting){ console.log(greeting+' '+name); } return displayName; } var myFunc = User('Kartik'); myFunc('Welcome '); //Output: Welcome Kartik myFunc('Hello '); //output: Hello KartikIn this code, We have an outer function User() which returns an inner function as displayName(), The inner function will have access to the variables in the outer function scope, even after the outer function has returned.
JS Libraries and Framework
find out all the JS libraries and framework here