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1.Describe null & undefined.

(null) is a special data type. Basically, we use it for an object. if we don't have any object in a variable you can define null as a value on that object and get output null in the console.

(undefined). you can get undefined in the console when you don't have any value. That means a variable without value always get output (undefined)

2.Describe Double equal (==) vs triple equal(===).

The deference between double equal and triple equal is , double equal can not check the data type and triple equal can check data type.

3.Describe Truthy vs Falsy.

some time you see true and false when you write condition in…

1.What is react?

react is a javascript library, React is not a framework. react is very powerful. by jsx you can write HTML and js in one page in react.

2.React DOM

DOM(document object model). All the interactivity in your website is handle by dom. for example you click a button on a website and something happens. that happens by dom


browser is not understand jsx, its understand the plane HTML, js. react ckompile the jsx then browser understand. we write HTML code in react.js, but in react.js those codes are not HTML code those are called jsx . and this is the power of…

1.primitive data type

javascript has two kinds of data types one is a primitive data type. You can write primitive data in your browser console. the primitive data type has 6 values i.Number, ii.string,iii.boolean, iv.null, v.undefined, vi.symbol.

2.reference data type

reference in another data type of javascript you can use it in your code, you can not write it in your browser console. reference data values (object, function)

3.expressions of javascript

expressions mean javascript can give you a response. but there is many thing in javascript can not give you a response like you asked javascript, about your girlfriend mind. on the other hand if you asked javascript about…

Array is a packet of object


using forEach you can get all the value from the array


what is slice? for example, you have an array, and inside the array have five animals' names (lion, monkey, dog, cat, mouse) and you don't like the dog inside the array. what you can do? yes, you can use slice. by using the slice method you can get the list of the value from the array excepted the dog.


parseFloat is a javascript number properti. it can convert a string to integer. if you have a number in a string, you can convert the number from string to integer by using parseFloat().

var age =“20 years”;


UI : 20;


toFixed is a method it have a internal power to fixed a number, for example user give you this(25.124586) . but you want only two number after the point.


const price= 12.666666


now you can get ; 12.66

javascript is a high-level programming language for making web applications. Basically, it is used for front-end-development interactivity, and it is also used in back-end development by node.js. javascript is so simple to use if you want to see the hello world in the web browser. then write this code below.

<h1 id=‘hello’></h1> This is a HTML tag

var hay = document.getEllementbyId(‘hello’);

hay.textContent = "Hellow World";

Some javascript math


ceil always gives you the up value. for example, you have a number (2.45)if you use ceil at the number you can get (3).


the floor always gives you the down value like, you have…

Saymon Shoab

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