Start a new journey with JavaScript

4 min readNov 2, 2020

Okay!
First of all Congratulation to you for taking a great initiative and that is learn about something. so congratulation again.

Let's began with a short introduction to javascript.

In 1995, JavaScript was created by Brendan Eich. At this time he was an engineer at Netscape. JavaScript was first released with Netscape 2 early in 1996. It was originally going to be called LiveScript, but it was renamed JavaScript which is a marketing decision that attempted to capitalize on the popularity of Sun Microsystem’s Java language — As if two having very little in common. This has been a make a wellspring of disarray from that point forward.

JavaScript syntax is based on C and Java languages. Let’s start off by looking at the building blocks of any language: the types. JavaScript programs manipulate values, and those values all belong to a type. JavaScript’s types are:

Number
String
Boolean
Symbol (new in ES2015)
Object
Function
Array
Date
RegExp
null
undefined

10most important topic will be given below for a better idea about javascript

Variables

There are three types of variable in javascript : let, const, or var.

let is used in a block-level variable :

let a;
let name = 'Dihan'; //Dihan
// myFunction is *not* visible out here

for (let myFunction = 0; myFunction < 5; myFunction++) {
  // myFunctionis only visible in here
}

// myFunctionis *not* visible out here

const allows you to declare in once in the entire code and it never changes.

const a = 'Dihan'; // variable a is set 
a = 'ábir'; // will throw an error because you cannot change a constant variable.

Operators

JavaScript’s numeric operators are +, -, *, / and %.

`Math`

There is also a built-in object that is called Math that provide us some advanced mathematical functions which are given below:

Math.sin(3.5);
var circumference = 2 * Math.PI * r;---console.log(3 / 2);             // 1.5, not 1
console.log(Math.floor(3 / 2)); // 1console.log(Math.ceil(3 / 2)); // 2

`parseInt()`

If you need to convert a string to an integer then we can use the built-in function calledparseInt() . This takes the base for the conversion as an optional second argument( this is mandatory to provide always):

parseInt('123', 10); // 123
parseInt('010', 10); // 10parseInt('010');  //  8
parseInt('0x10'); // 16

splice()

This ‘’splice() ‘’ method takes three-parameter, first for all targeted the index number, second for how many items you want to delete/update or replace and the third parameter is what you want to insert.

let names = [‘dihan’, ‘abir’, ‘murad’];
let name = names.splice(2,0, ‘robin’, ‘jalal’ );
console.log(name);


let names = ['dihan', 'abir', 'murad'];
let name = names.splice(2,0, 'robin', 'jalal' );
console.log(name);

JS String : charAt( )

chatAt function takes an integer number as a parameter which is called “index”and return a new char corresponding to the “index” value.

const text = ‘this is chat’;
const index = 3;
console.log(text.charAt(index));// output : i

Map

Map is a collection of keyed data items, just like an Object. But the main difference is that Map allows keys of any type.

Methods and properties are:

new Map() – creates the map.
map.set(key, value) – stores the value by the key.
map.get(key) – returns the value by the key, undefined if key doesn’t exist in map.
map.has(key) – returns true if the key exists, false otherwise.
map.delete(key) – removes the value by the key.
map.clear() – removes everything from the map.
map.size – returns the current element count.

let map = new Map(); 
 map.set('1', 'str1');   // a string key 
map.set(1, 'num1');     // a numeric key 
map.set(true, 'bool1'); // a boolean key  
// remember the regular Object? it would convert keys to string // Map keeps the type, so these two are different: 
alert( map.get(1)   ); // 'num1' 
alert( map.get('1') ); // 'str1'  
alert( map.size ); // 3

Set

A Set is known as a special type of collection where each value may occur only once at a time.

Its main methods are:

new Set(iterable)
set.add(value)
set.delete(value)
set.has(value)
set.clear()
set.size

Iteration over Set

let set = new Set(["oranges", "apples", "bananas"]);
for (let value of set) alert(value);  // the same with forEach: 
set.forEach((value, valueAgain, set) => {   alert(value); });

Arrays

Array in JavaScript is really an extraordinary kind of article. They work a lot like customary articles. However, they have one common property called ‘length’. This is consistently one more than the most elevated record in the exhibit.

var a = new Array();
a[0] = 'Rakib';
a[1] = 'Nahid';
a[2] = 'Nayeem'
a[3] = 'Nayeem';
a.length; // 4