JavaScript essentials for React developers.md

JavaScript essentials for React developers

Variable Declaration

var - Used to declare variables but the scope of variables is function block. if declared globally, scope is global

let - Used to declare variables but variables are block scoped

const - Used to declare variables but variable can't be reassigned. Declared variables are immutable. const variables are also block scoped

Classes

function keyword is not used to declare functions. We don't need to have the word function for declaring methods

We can't assign properties as we do in methods. We initialize them using constructor method

constructor method is special method which is called on creation of objects and used to initialization

this is always point to current object

Inheritance

Inheritance is the mechanism of creating a new class(child class) from another class(parent class)

super() method is mandatory to call if we have declared custom constructor for Child Class, else not required

super is used to call Parent Class methods inside Child Class

Child Class will have access to all parent class methods

this will always point to current object

Arrow functions

this in arrow functions always inherits this object from the context in which code is defined. We don't need to do that = this or self = this or .bind(this)

this always points to current objects in arrow functions

Array.map()

This method doesn't modify original array, it returns a new array

Template Literals

Multi-line Strings

Object Destructuring

Spread Operator

Spread operator is used to extract all array items or object properties. To create objects we use {...} and to create arrays we use [...]

Modules

We use export keyword before class and variables to make them available for other modules. import keyword is used to import variables or classes from other modules