Skip to content

Courses
Tutorials
Practice
Contests

TypeScript Tutorial
TS Exercise
TS Interview Questions
TS Cheat Sheet
TS Array
TS String
TS Object
TS Operators
TS Projects
TS Union Types
TS Function
TS Class
TS Generic

How to Create Deep Readonly Type in Typescript?

How to declare nullable type in TypeScript ?

Last Updated : 15 Oct, 2024

Comments

Improve

Suggest changes

Like Article

Like

Report

In vanilla JavaScript, there are two primary data types: null and undefined. While TypeScript previously did not allow explicit naming of these types, you can now use them regardless of the type-checking mode.

To assign undefined to any property, you need to turn off the --strictNullChecks flag. However, with this flag enabled, you cannot assign undefined to members that do not have the nullable operator.

This update in TypeScript enhances type safety, allowing developers to explicitly handle cases where values may be absent, ultimately reducing runtime errors and improving code quality.

Example: The below example represents what happens if the --strictNullChecks flag is enabled and the following code is executed.

javascript

interface Student { name:string; age:number; } let s: Student = { name:'Ajay', age:null }

It will throw the below error:

Type 'null' is not assignable to type 'number'

This error won't appear if we have --strictNullChecks flag turned off. The strictNullChecks flag protects from referencing nulls or undefined values in the code. It can be enabled by adding the -–strictNullChecks flag as an option to the command-line compiler or adding it to the tsconfig.json file.

There is a difference between the Nullable type and "optional". In "optional", we provide some default value to the member or let it not be considered as a member. However if any member is assigned optional and then still assigned a value as "null" or "undefined", then it will throw an error.

javascript

interface Student { name:string; age?:number; } let s: Student = { name:'Ajay', age:null }

How to Create Deep Readonly Type in Typescript?

techni621

Improve

Article Tags :

JavaScript
Web Technologies
TypeScript
JavaScript-Misc

Similar Reads

How to check interface type in TypeScript ?

Typescript is a pure object-oriented programming language that consists of classes, interfaces, inheritance, etc. It is strict and it statically typed like Java. Interfaces are used to define contacts in typescript. In general, it defines the specifications of an entity. Below is an example of an in

How to Check Types in Typescript?

Checking types in TypeScript involves methods like typeof for primitive types, instanceof for class instances, and custom type guards for complex type validation. These techniques help ensure variables are correctly typed, improving code safety, and readability, and preventing runtime errors.Here ar

How to express a Date Type in TypeScript ?

In TypeScript, the Date object is used to handle dates and times. To express a Date type, declare a variable with the type annotation Date and assign it a date value. This allows for precise date manipulation and formatting in your TypeScript code. Ways to Express Date Type in TypeScriptTable of Con

How to Create Deep Readonly Type in Typescript?

In TypeScript, the readonly access modifier is a powerful tool that ensures immutability by marking properties of a class as immutable. Once a property is markedreadonly, it cannot be reassigned. This is highly useful for maintaining consistent and safe data structures, especially in scenarios such

How to define Singleton in TypeScript?

In this article, we will learn about the Singleton in TypeScript. A singleton is a class that always has only one instance of it at the global level. If more than one instance is created then they all will refer to the same instance and changes in the properties of one instance will reflect in the p

How to Exclude Property from Type in TypeScript ?

In Typescript, sometimes we need to exclude a property from a type when we want a similar type with some properties excluded or if we want to remove a property from the type. There are several approaches to exclude properties from a type in typescript: Table of Content Using Mapped Types with condit

How to use Type Guards in TypeScript ?

Here are the methods to use type guards in TypeScript: 1. Using typeof Type GuardsThe typeof operator checks the type of a variable, primarily for primitive types like string, number, boolean, etc. [GFGTABS] JavaScript function processValue(value: string | number) { if (typeof value === 'string

How to Return a Union Type in TypeScript ?

In TypeScript, a union type is a powerful way to express a variable that can be one of several types. Union types are used when a function or variable is expected to support multiple types of input. Union types are defined using the pipe (|) symbol between two or more types. This indicates that a va

How to enforce strict null checks in TypeScript ?

In Typescript to enforce strict null checks in tsconfig.json file, we need to enable "strictNullChecks" to true. When "strictNullChecks" is false, the language generally ignores variables of type null and undefined. If null and undefined is used in places where a definite value is expected, it raise

How to Declare Variables in TypeScript ?

In TypeScript, a variable can be defined by specifying the data type of the value it is going to store. It will store the values of the specified data type only and throws an error if you try to store the value of any other data type. You can use the colon syntax(:) to declare a typed variable in Ty

Corporate & Communications Address:

A-143, 7th Floor, Sovereign Corporate Tower, Sector- 136, Noida, Uttar Pradesh (201305)

Registered Address:

K 061, Tower K, Gulshan Vivante Apartment, Sector 137, Noida, Gautam Buddh Nagar, Uttar Pradesh, 201305

Advertise with us

Company
About Us
Legal
Privacy Policy
In Media
Contact Us
Advertise with us
GFG Corporate Solution
Placement Training Program

Languages
Python
Java
C++
PHP
GoLang
SQL
R Language
Android Tutorial
Tutorials Archive

DSA
Data Structures
Algorithms
DSA for Beginners
Basic DSA Problems
DSA Roadmap
Top 100 DSA Interview Problems
DSA Roadmap by Sandeep Jain
All Cheat Sheets

Data Science & ML
Data Science With Python
Data Science For Beginner
Machine Learning
ML Maths
Data Visualisation
Pandas
NumPy
NLP
Deep Learning

Web Technologies
HTML
CSS
JavaScript
TypeScript
ReactJS
NextJS
Bootstrap
Web Design

Python Tutorial
Python Programming Examples
Python Projects
Python Tkinter
Python Web Scraping
OpenCV Tutorial
Python Interview Question
Django

Computer Science
Operating Systems
Computer Network
Database Management System
Software Engineering
Digital Logic Design
Engineering Maths
Software Development
Software Testing

DevOps
Git
Linux
AWS
Docker
Kubernetes
Azure
GCP
DevOps Roadmap

System Design
High Level Design
Low Level Design
UML Diagrams
Interview Guide
Design Patterns
OOAD
System Design Bootcamp
Interview Questions

Inteview Preparation
Competitive Programming
Top DS or Algo for CP
Company-Wise Recruitment Process
Company-Wise Preparation
Aptitude Preparation
Puzzles

School Subjects
Mathematics
Physics
Chemistry
Biology
Social Science
English Grammar
Commerce
World GK

GeeksforGeeks Videos
DSA
Python
Java
C++
Web Development
Data Science
CS Subjects

@GeeksforGeeks, Sanchhaya Education Private Limited, All rights reserved

We use cookies to ensure you have the best browsing experience on our website. By using our site, you acknowledge that you have read and understood our Cookie Policy & Privacy Policy

Improvement

Suggest Changes

Help us improve. Share your suggestions to enhance the article. Contribute your expertise and make a difference in the GeeksforGeeks portal.

geeksforgeeks-suggest-icon

Create Improvement

Enhance the article with your expertise. Contribute to the GeeksforGeeks community and help create better learning resources for all.

geeksforgeeks-improvement-icon

Suggest Changes

min 4 words, max Words Limit:1000

Thank You!

Your suggestions are valuable to us.

What kind of Experience do you want to share?

Interview Experiences

Admission Experiences

Career Journeys

Work Experiences

Campus Experiences

Competitive Exam Experiences