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  1. What are truthy and falsy values?

Answer: In boolean context, a conditional variable value that returns true is called truthy value. All values are truthy values unless it declared as falsy values. Falsy values are 0, empty string, undefined, null, NaN, false.

2. Difference Between Undefined and Null?

Answer: Undefined means not defined. It is a type. It means declaring a variable but no value assigned. When I access a property of an object but this property is not declared then I get undefined. On other hand, Null means not exist. It is an object. …


As a developer, you should know this fact about React.

  1. Not a Framework

Sometimes we tell that React is a Framework. It was absolutely wrong. React is a JavaScript Library. Using React you can build your User Interface with Component. React will not help you with server communication, routing, translations and so on. React is so thin and easily worked with any 3rd party libraries.

2. JSX

JSX is basically providing syntactic sugar for the React.createElement(component, props, …children) function. JSX stands for JavaScript XML. JSX allows us to write function in a HTML tag like syntax. …


This writing is about some facts about JavaScript that you should know before written code. So, I assume you have some basic knowledge about programming language.

Let's start…

We all know about data types, aren’t we? Basically, in JavaScript, there are two types of data types. Those are primitive and non-primitive.

Primitive Type

Primitive types are nothing just numbers, strings, and other things. All primitive types have common things that do not affect code. You might be want to know how many types primitive value is hidden in the JavaScript. After almost 25 years of research, the scientist discovers such…


Before going to the depth of JavaScript number, string and array methods, we should know that what is Number, String and Array. Right?

A. Number

The JavaScript Number type is a double-precision value that means it can represent fractional values like — 2.5, 2.0, 5.982. But there are some limitations to what it can store. It can store only 17 decimal places of precisions.

i. Number Methods

  1. Number.isNaN() : isNaN() methods takes values and determine the passed value is NaN or Not. ‘NaN means Not a Number’. It return only true or false.

Debashis Ray

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