Javascript ES12 / ES 2021 Features

Separator for numeric literals:

We can use underscore as a separator for numeric literals . It is good to use for amount. It improves readability. 

Before :

let amount = 100000;

After:

let amount = 1_00_000;

let price = 5_678.97

• You can use underscore with both integers, decimal values.
• You must use underscore only between digits. You get an error if you use it before or after digits.
• Below are valid declarations.

let amount1 = 10_000;

let amount2 = 5_876.98;

Below are invalid declarations 

let amount1 = _1000;

let amount2 = 1000_;

let amount3 = 1000_.56;

You get below error . 

Logical assignment operators: 

Logical Nullish assignment(??=):

Nullish coalescing operator returns right side value if left side value is either null or undefined.

let fullName;

let fName = fullName??='Narayana Bojja';

console.log(fName);

Output:

Narayana Bojja

Here fullName variable doesn't have any data . It's value is undefined . So, It assigns right side value to fName variable.

let fullName='Bojja Narayana';

let fName = fullName??='Narayana Bojja';

console.log(fName);

Output:

Bojja Narayana

Here fullName variable has data . It assigns same data to fName variable. This operator useful if you want to make sure variable has some data.

Logical And Assignment (&&=):

It evaluates from left to right . It assigns value only if left side expression is true.

let x = 10;

let y = 20;

x &&= y;

console.log(x);

Output: 20

Here x has value . It will be evaluated as true. It assigns y value to x.

let x ;

let y = 20;

x &&= y;

console.log(x);

Output: undefined

Here x doesn't have value . It will be evaluated as false. It doesn't assign y value to x. This operator useful if you want to re assign variable with some data.

Logical OR Assignment (||=):

It works opposite to Logical And operator. If left side expression is false, it assigns right side value. 

let x ;

let y = 20;

x ||= y;

console.log(x);

Output : 20

Here x doesn't have value . It will be evaluated as false. It  assigns y value to x.

let x = 10;

let y = 20;

x ||= y;

console.log(x);

Output: 10

Here x has value . It will be evaluated as true. It doesn't assigns y value to x. This operator useful if you want to assign variable with some data in order to avoid any error.

String replaceAll method:

At present , there is replace method which replaces only first occurrence of  a string with another string.

let fullName = "narayana narayana narayana"

fullName = fullName.replace('narayana', 'kavitha');

console.log(fullName);

Output:

kavitha narayana narayana

To replace all occurrences , we need to use regular expression.

let fullName = "narayana narayana narayana"

fullName = fullName.replace(/narayana/g, 'kavitha');

console.log(fullName);

Output:

kavitha kavitha kavitha

We can now use replaceAll method to replace all occurrences of a string with another string.

let fullName = "narayana narayana narayana"

fullName = fullName.replaceAll('narayana', 'kavitha');

console.log(fullName);

Output:

 kavitha kavitha kavitha

I hope you have learned something new today. Please feel free to leave a comment below. Happy Coding 😃

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