Javascript Overview

Ataur Rahman
2 min readJul 27, 2021




In Javascript Number are two type:

  1. Number
  2. BigInt.

String:In javascript strings is sequences of unicode chareacters.

Javascript have some build in method to manipulate the strings. Ex:

“hello”. charAt(0);Output :h

“hello”.toUpperCase();Output :HELLO

Other types:

Null:The obsence of Object value.

Undefined:A variable is initialized but value is not assigned yet.

Boolean:True And False.


In javascript variable declare for three keyword :

Let,const and var.

Let and const are block-scope variable.

Var is available in function scope.


Javascripts math operator +, —, *,/ and % which is called remainder also called moduls.

Value assigned using =,

Increment ++,Decrement--,

For strings concatenation using ‘+’ operator.

Comparisons operators are <,>,<=,>=.

Control loops

While loop the body executed at least once.It has aslo do……while loop.

For loop give us to control the loop in single line of code.

Swich statement use to swich multiple brances.


Javascript object is name and value pair collection. Here name is string value can be any type of data or function also.

For empty object

Let obj = new Object ();

Or, let obj = {};

For access the object value using dot notation and 3rd bracet.




Javascript array is a kind of object. To declers object we use [].Array has a build in magic property called length.


A JavaScript function is a block of code designed to perform a particular task.

A JavaScript function is executed when "something" invokes it (calls it).

Function javascriptFunction (para1,para2){task

return something }

Call a function