JavaScript Ecma Script-6 important topic for beginners

3 min readMay 6, 2021

Here I am going to discuss Ecma script-6's most important parts to beginners. Here we go…

Block-Bindings:

we declare variable all kinds of programming language such as c,c++, java, and javascript also. In javascript, we declare a variable in many ways. Before Es-6 came, we used var to declare a variable. Block means it can not access outside the function or where it is declared. Declare a variable Like =>

var sum=0;

But when ES-6 came, we declare a variable in let and const.

let sum=0;

const sum = 0;

let means this value can be changed but const means this is can not be changed.

Var declaration and hoisting:

When we declare a variable using var and it is top of the function and where the actual declaration occurs this is called hoisting. Example =>

function sum (a, b){

var total = 0;

total = a + b;

return total;}

Block Binding in loop:

Example:

for( var i = 0; i≤5; i++){

var element = element[i];

console.log(element);}

let and const declaretion in loop:

In ES-6 we can use let and changed var. Like =>

for( let i = 0; i≤5; i++){

let element = element[i];

console.log(element);}

Function in ES-6:

When ES-6 has come, the Whole function declare pattern changed, and before we declare function it was like =>

function sum (a, b){

var total = 0;

total = a + b;

return total;}

But in Es-6 we can use the arrow function to declare a function.it like =>

let sum = (a, b) => a + b;

Rest parameters:

It is declared by three dots and it has two restrictions and one is there can be only one rest parameter, and the rest parameter must be last.

function checkArguments(…args){// your code

}

The spread operator:

It is the closely same of rest parameters. the spread operator allows you to specify an array that should be split and have its items passed in as separate arguments to a function. we can use Math. max for an example =>

let a = 10,b = 15;

console.log(Math.max(a,b));

Ans is 15;

Block-Level Functions:

“use-strict”;

if(true){

console.log(‘block’);

function test(){

console.log(‘test’);

}

Arrow function :

It is more efficient and easy to use example =>

let sum=(a,b)=>a+b;

In Array, we can use arrow function in many ways like =>

const number=[1,2,3,4,5];

console.log(number.map(num => number.length));\

Tail call optimization:

A tail call is when a function is called as the last statement in another function, like this =>

function doSomething(){

return doSomethingElse();}//tail call

How to Harness Tail Call Optimization:

It happens when we using recursive. Factorial example given below =>

function factorial(n){

if(n ≤1){

return 1;

}

else {

return n* factorial (n-1);

}

this is not an optimization code , because multiplication must happen after the recursive call to factorial().Optimazation process =>

function factorial(n, p=1){