If you declare a variable but can’t set value. it show you undefine that means undefine is where a variable can’t set a value.

basically null is a variable value. you can define any type of value in a variable.
example:
let test1 = you can define string;
let test2 = you can define number;
let test3 = you can define object;
In the same way,
let test4 = null;
null means nothings. it’s falsey value.

Function Scope vs Block Scope

Function scope is created when you declare variable inside a function. The variable is visible only within the function…


I will be discus about React.js basic. In my concept React.js is a library not a framework. Basically it works with JavaScript. If you know JavaScript basic you can easily handle React.js. React.js have many parts. If you get this parts. You can easily upstand the main concept of React.js. So let’s start discus about of every parts of React.js.

Library not Framework

Vue or Angular are frameworks where decisions are made for you. But React is just a library and you need to make all decisions by yourself. It focuses on helping you to build user interfaces using components.


Cross Browser.

Cross Browser is a testing process there a website or a web apps is tested in different browser,
different website, different device and find out the bugs.

JavaScript Errors.

Somehow every programmer makes some mistake when he/she makes instruction then occurs an error.
if an error occurs JavaScript has a default error catch system.

The system is try, catch, throw and finally.

The try statement give you test a block of code for errors.

The catch statement give you handle the error.

The throw statement give you create custom errors.

The finally statement give you execute code, after…


Today I want to discuss JavaScript core fundamental JavaScript Strings.

JavaScript String

Basically JavaScript strings are used for storing and manipulating text and
It is written inside single qoutes and double qoutes.

Examples:
let str = ‘Hello World’;
let str2 = “What is your name?”;

JavaScript belongs to some built-in methods.If you ask what is methods, I just tell you it is process that make
easyer in some work. So JavaScript string also have methods.

1. indexOf()
2. slice()
3. toUpperCase()
4. toLowerCase()
5. concat()
6. split()

The indexOf() method returns position of specified string.

examples:
let str =…

Robiul Islam

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