https://github.com/amolpalwe2002/learn-javascript
https://github.com/amolpalwe2002/learn-javascript
Last synced: 4 months ago
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- Host: GitHub
- URL: https://github.com/amolpalwe2002/learn-javascript
- Owner: amolpalwe2002
- Created: 2024-05-03T10:17:55.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-05-10T05:21:16.000Z (over 1 year ago)
- Last Synced: 2025-01-03T08:30:32.569Z (12 months ago)
- Language: HTML
- Size: 4.88 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
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README
# Java is as similar to Javascript, as a Car is similar to Carpet
## What is Javascript Engine?
1. V8
2. SpiderMonkey
```
// print on the console
console.log("Hello World");
```
## What ES(ECMAscript) version is good for us
--> ES6
## Variables and Datatypes in JS
var, let and const
```
// declaring and initialising variables
var fullName = "Amol Palwe";
var isLoggedIn = true;
var loggedCount = 14;
console.log(loggedCount);
console.log("loggedCount");
var paymentMethod;
paymentMethod = "Credit Card";
```
## Creating user signup
```
const UID = "1234567890";
// Assignment to const variable
// UID = "0987654321";
var firstName = "John";
var lastName = "Doe";
var email = "pCJ0h@example.com";
var password = "123456";
var verifyPassword = "123456";
console.log(`Hello ${firstName} ${lastName}!
You can email me at ${email} and
my UID is ${UID}.`);
```
## Operators
"+", "-", "*", "/", "%", ">", "<"
--> Math library
--> Operator precedence
## What are conditionals in JS
```
var temperature;
// TODO: Go to GOOGLE and fetch data
temperature = 20;
if(temp < 30){
console.log("it's cold outside");
}else{
console.log("it's hot outside");
}
// Allow user to logIn if:
// 1. logged in form email
// 2. logged in form Google
// 3. logged in form facebook
var loggedInUsing = "Instagram";
if(loggedInUsing == "Google" || loggedInUsing == "facebook" || loggedInUsing == "email"){
console.log("You are logged in using " + loggedInUsing);
}else{
console.log("You are not logged in");
}
```
## Ternary Operator
```
var age = 20;
var result = age>18 ? "You can vote" : "You can't vote";
console.log(result);
```
## Switch case
```
// Authorization differnt users
// 1. Admin - full-access
// 2. subAdmim - create/delete content
// 3. users - read only access
var user = "subAdmin";
switch (user) {
case "admin":
console.log("Full access");
break;
case "subAdmin":
console.log("Create/delete content");
break
default:
console.log("Read only access");
break;
}
```
## Coercion and Falsy values
- falsy values (considered as false)
1. undefined
2. null
3. NaN
4. 0
5. ""
## Functions in JS
```
function sayHello(name = "Amol") {
console.log(`Hello ${name}`);
}
sayHello("John");
sayHello("Carry");
sayHello();
function namaste(name = "Amol") {
return `Namaste ${name}`;
}
console.log(namaste("John"));
/*
Define a function to answer the role of the user
1. Admin - full access
2. SubAdmin - access to create/delete courses
3. User - read only access
4. other - no access
*/
function roleChecker(name, user) {
if (user === "admin") {
return `Full access for ${name}`;
} else if (user === "subAdmin") {
return `create/delete courses for ${name}`;
} else if (user === "user") {
return `read only access for ${name}`;
} else {
return "`No access for ${name}`";
}
}
console.log(roleChecker("Deep", "subAdmin"));
```
## Context in JS
```
// Execution context
console.log(fullName);
sayHello("Amol Palwe");
var fullName="Amol";
function sayHello(name){
console.log(`Hello ${name}`);
}
```
## Scope chaining in JS
```
var fullName = "Amol Palwe";
console.log(`Hello ${fullName}`);
function sayHello1(fullName = "John Doe") {
console.log(`Hello ${fullName}`);
}
function sayHello2(fullName = "Carlos") {
console.log(`Hello ${fullName}`);
}
sayHello1();
sayHello2();
```
## THIS in JS
```
console.log(this);
let user = {
name: "John",
age: 30,
isAdmin: true,
getUserName: function(){
console.log(this);
function sayHi(){
console.log(this);
}
sayHi();
}
}
user.getUserName();
```
## Array in JS
```
var arr = ["Amol", "Palwe", "Java", "Script"];
console.log(arr);
arr.pop();
console.log(arr);
arr.push("Hello");
console.log(arr);
arr.unshift("Hi");
console.log(arr);
arr.shift("Hi");
console.log(arr);
console.log(arr.length);
console.log(arr.indexOf("Java"));
```
## Callback and Arrow function
```
var isEven = (number) => {
return number % 2 === 0;
}
// console.log(isEven(4));
console.log([8, 2, 6, 4].every((e) => {
return e % 2 === 0;
}));
```
## fill and filter methods
```
const arr = [1,2, 3, 4, 5, 6, 7, 8, 9, 10];
console.log(arr.fill("A", 2, 6));
console.log(arr.filter((num) => {
return num>=5;
}));
```
## slice and splice methods
```
const users = ["ted", "john", "amol", "deep", "Carry", "Lorem"];
// console.log(users.slice(1, 3));
const arr = users.splice(1, 3, "edited");
console.log(arr);
console.log(users);
// console.log(users.splice(1, 3, "edited"));
```
## Objects in JS
```
let user = {
firstName: "Amol",
lastName: "Palwe",
age: 20,
email : "amol@gmail.com",
courseList : [],
buyCourse : function (courseName){
this.courseList.push(courseName);
}
}
user.buyCourse("Javascript");
user.buyCourse("HTML");
console.log(user.email);
console.table(user);
console.log(user);
```
## For Loop in JS
```
// for(let i=0; i<10 ; i++){
// console.log(i);
// }
const states = ["Maharashtra", "Goa", "Karnataka", 1947, "TamilNadu", "Kerala"];
for(let i=0; i (console.log(state)));
```
## forIn and forOf loop in JS
```
// forOf is used for arrays
const companies = ["Google", "Amazon", "Facebook", "Apple"];
for(let company of companies){
console.log(company);
}
// forIn is used for objects
let user = {
firstName: "Amol",
lastName: "Palwe",
age: 20,
email : "amol@gmail.com",
courseList : [],
buyCourse : function (courseName){
this.courseList.push(courseName);
}
}
for(let key in user){
console.log(key, user[key]);
}
```
## DOM - Document Object Model
```
// Select elements on web page
console.log(document.getElementById("heading").innerHTML);
let heading = document.getElementById("heading");
heading.innerHTML = "Jay Radhe Jay Krishna";
```