Typescript dynamic object property access. Each method is explained with simple examples to .

Typescript dynamic object property access. Feb 28, 2024 · Use an interface or a type alias to type a nested object in TypeScript. type Obj = Readonly When working with JavaScript or TypeScript, you may have encountered situations where you need to access object properties using dynamic keys. This allows the creation of flexible data structures where properties can be added or accessed using variables, providing more versatile type definitions. After several years of using TS, I normally still have to Google for examples when I’m doing something similar to what you’re trying, it can be v annoying. Jul 2, 2025 · The second approach using TypeScript's advanced type system ensures that developers working with deeply nested objects can enjoy both the flexibility of dynamic key access and the type safety that TypeScript provides. For example, a common JavaScript pattern is to pick a subset of properties from an object: Nov 8, 2019 · Fully utilizing static types, with all the safety they provide, can be a bit tricky when dealing with dynamic data — like JSON from an API call. Jan 21, 2020 · I read from the TypeScript documentation, that you can't access properties from the type unknown: // No property accesses, element accesses, or function calls function f11(x: unknown) { x. That’s because there is no guarantee that those keys are present on the object. Even though I believe I do the appropriate checks, I still get a type error. Example 3: Creating a Custom Utility Type Index signatures are essential in TypeScript for creating complex utility types because they allow for flexible and dynamic data structures while maintaining type safety. 3:04 A really common pattern in JavaScript is assigning things to an object with dynamic keys, and this allows you to do it. The original source and a detail explanation of the function can be found in the Typescript documentation. ” Likewise xPos: number creates a variable named number whose value is based on the parameter’s xPos. A best-practice solution/pattern for this would really help me along. Oct 14, 2023 · Defining properties in TypeScript objects allows us to store and access data related to the object's state. In the code block below, you can see that there are two errors thrown by typescript when I try to access this new properties. Nov 3, 2024 · 1. This blog post will guide you through the fundamental concepts, usage methods, common practices, and best practices for accessing properties of nullable objects in TypeScript. - Accessing object properties dynamically. Dynamic object types allow you to create objects with properties that are determined at runtime, providing flexibility and versatility in your code. Jul 26, 2019 · I don’t really understand how to access an object property dynamically using a variable. To iterate over them is a common task for manipulating or accessing the stored data. In conclusion, the ability to access properties via their name and bracket notation is a powerful and flexible feature of Javascript Oct 24, 2024 · Learn how to dynamically assign properties to objects in TypeScript while maintaining type safety with seven effective approaches, including explicit type declaration, object index signatures, and the use of utility types like Record and Partial. Lets assume we have the following example. Nov 23, 2024 · Learn how to handle dynamic property names in TypeScript with type safety using index signatures, mapped types, and conditional types in this simple guide. @AlexeySh. It takes a property name prop and returns an accessor function. , it stays the same all through your application. Let's look at how to do this in TypeScript. Learn how to efficiently access object properties in TypeScript using bracket notation with dynamic keys, simplifying your code and improving type safety. May 7, 2015 · If TypeScript is a strict superset of JavaScript, why is dot notation on an arbitrary object erroneous? I have JS code that I want to convert over to TS for better type safety, but all access using May 7, 2024 · - Creating dynamic data structures. Oct 27, 2024 · Conclusion Understanding how to work with dynamic object keys in Typescript opens up a world of possibilities for creating more flexible and dynamic code. Related Article: How to Convert a String to a Number in TypeScript Creating an Object with a May 6, 2022 · I am trying to assign a value from an object of type TestInterface to another object of type TestInterface by accessing it with a dynamic key of type keyof TestInterface. We will explore both ways to get access to the object property & will understand its basic implementation with the help of examples. In this tutorial, you learn how to use the TypeScript getters and setters to control access to properties of a class. These properties can be used to represent real-world entities, such as people, products, or any other data structure. Mar 22, 2023 · How to - TypeScript How to - use dynamic keys with TypeScript objects By using index signatures, the Record utility type, mapped types, and nested types, you can define and manipulate objects with dynamic keys efficiently and safely. This blog post will guide you through the process of getting a property by variable in TypeScript, providing you with the necessary knowledge and examples to master this technique. Jul 23, 2025 · In TypeScript, we can get an object value by key by accessing the specific properties within the objects of the dynamic type. Mar 19, 2025 · Accessing object properties, especially dynamically, is a common cause of errors in programs. My goal is to get all the keys of the given type. Whether you need to access, modify, or create object properties on the fly, mastering this concept will make you a more versatile Typescript developer. b?. object [key1] [key2]. Discover how to correctly perform dynamic property access on object methods in TypeScript to overcome common challenges. e. Whether you’re working with API responses, configuration objects, or data mappings, understanding index signatures is crucial for writing type-safe TypeScript code. Mar 11, 2024 · In TypeScript, index properties allow you to define objects that can hold a flexible set of properties, where the property names are not known in advance but can be determined dynamically. type StringArray = string[]; Apr 6, 2023 · Dynamically accessing object property in TypeScript Asked 1 year, 10 months ago Modified 1 year, 5 months ago Viewed 330 times Dec 1, 2016 · Is there any way to have dynamic object properties in a TypeScript class, and add dynamic Typings in for TypeScript? I have seen similar questions but none with a complete example like this - bobbyhadz / typescript-access-object-property-dynamically Public Notifications Fork 0 Star 0 TypeScript is a language for application-scale JavaScript development. Apr 15, 2024 · Introducing TypeScript into your JavaScript app introduces some rigidity to your code – you lose the complete flexibility of JavaScript, but gain a lot of robustness and reliability in your code. Suppose you have a type Feb 14, 2024 · This can be particularly useful when dealing with objects that have a mix of known and dynamic properties. However, the responses you're observing have some common properties and some uncommon properties: Jun 15, 2025 · Nullable objects can be `null` or `undefined`, and trying to access properties on them without proper handling can lead to runtime errors. Aug 16, 2021 · Is it possible to get the type of an object property using a variable? I. Understanding TypeScript Dynamic Object Type When working with TypeScript, one of the powerful features it offers is the ability to define dynamic object types. So I would like to find a way to have all the keys of a nested object. So the JSON. But I get an error: "Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{}'" I have t In an object destructuring pattern, shape: Shape means “grab the property shape and redefine it locally as a variable named Shape. This guide will provide you with the r I also use it to transfer data from server to client and that dynamic object tells it which keys it should write and read. TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. . What's reputation and how do I get it? Instead, you can save this post to reference later. when the property name is a variable). Feb 20, 2022 · I want to sort an array of objects with dynamically created properties. In Angular 8 I created an object from a JSON, there is a dynamic property, I do not know the name of it before runtime. The syntax `obj [key]` allows you to dynamically access a property of an object, where `obj` is the object and `key` is a variable representing the property name. --- Always keep your actual property names as all lower-case (or upper), and then convert when querying. Learn how to dynamically assign properties to an object in TypeScript with this helpful guide. defineProperty. If you still want to keep the powerful typechecking feature of TS, choose this MyEnum[x as keyof typeof MyEnum] typeof MyEnum will create an interface that represents the MyEnum object behind the scene and keyof will return a union of string literals, each one is the key in the MyEnum object (in other words, keyof will return a list of key s of a given Mar 13, 2024 · This pattern is scalable and can be extended to include other dynamic properties if needed, by adding more nested objects or arrays with their specific types. c; I. Of course, I can change this second property to anything I want to. the T in the first 3 examples is actually any type you want that your properties should have. Mar 6, 2024 · In this tutorial, Learned How to add dynamic properties to an object javascript and typescript examples using any type, index type, record type, and interface extends With strict null checking enabled, TypeScript forces you to ensure that an object is defined before accessing its property. parse () method is declared in TypeScript's library to return the intentionally loose any type. Dynamic Flexibility with keyof and Generic Constraints Using keyof with generics allows you to define types that depend on the properties of another type. Jan 19, 2023 · Handling Dynamic Property Typings with TypeScript January 19, 2023 The scenario We've all been there. Feb 27, 2024 · A step-by-step guide on how to dynamically access an object's property in TypeScript. I have checked the following, but I can't find the answer I am looking for: TypeScript dynamic object prope Apr 26, 2023 · There's a general situation that the TypeScript compiler can't do much to strongly type JSON-strings, especially strings that are only known at runtime (say, from a server response). Oct 20, 2021 · Also, bear in mind that like with everything TypeScript you'll have an imprecise reflection of which properties are enumerable own properties (see #9726), which might be a signficantly narrower set than what you and TypeScript would expect to be available on ModelBase<Foo>. May 28, 2021 · How to access JSON object value with dynamic key in typescript with angular Asked 4 years, 3 months ago Modified 4 years, 3 months ago Viewed 11k times Oct 20, 2023 · A short little article about TypeScript’s inference system and how we can pre-define custom keys, dynamically This may have duplicates, there may be articles already written about this. Jul 23, 2025 · In TypeScript, objects with dynamic keys are those where the key names are not fixed and can be dynamically determined at runtime. I have taken a Chapter 6 Objects Learn TypeScript's advanced type system: Extending objects, intersection types, interfaces, dynamic keys, and utility types. Dec 3, 2021 · You have to ensure that prefixIconName will only be one of the keys of svgs – TS is correct here, but dynamic object access is normally a pain point when learning TS. Feb 2, 2024 · This tutorial demonstrates how dynamic properties can be added to an object in TypeScript. Mar 10, 2023 · I would like to make this JavaScript function type safe. Nov 29, 2021 · How to access object property using variable in TypeScript? Asked 3 years, 5 months ago Modified 3 years, 5 months ago Viewed 3k times When working with TypeScript, dynamic key access is a powerful feature that allows you to access object properties dynamically at runtime. This guide provides a straightforward overview of different methods to access enum values in TypeScript, including bracket notation, dot notation, object lookup, and using Object. example: const obj = { var1: ‘value’ }; {var1} = obj ; var1 // value TypeScript is a language for application-scale JavaScript development. TypeScript helps prevent these issues by offering tools such as optional chaining, nullish coalescing, and type narrowing. As you learn TypeScript however, you’ll find a lot of ways to quickly build dynamic types – let's go through a few. Sep 18, 2019 · This function infers the type of the object T and casts the property name to the key type K, returning the property of the object using the given key T[K]. Example: Imagine you’re building a utility to access properties on an object. - Validating and checking the type of object keys. 7 now supports the optional chaining operator. This feature provides precise type information about properties or elements, enhancing type safety when accessing deeply nested structures or specific object keys. Each method is explained with simple examples to Jan 25, 2025 · Index signatures are one of TypeScript’s most powerful features for handling dynamic object properties. The Record Utility Type TypeScript provides a utility type exactly for the Use TypeScript properties to define object structures, ensure type safety, and control data access in objects, classes, and interfaces for better consistency. While it won’t change any behavior at runtime, a property marked as readonly Jul 23, 2025 · By declaring the object constructor, & then creating objects of the constructed type By using the Object. Jan 7, 2024 · In this tutorial, we explored how to convert JavaScript objects into TypeScript enums, offering developers a method to maintain readability, enhance type-safety, and leverage existing code. They allow you to specify the types of values that can be accessed via bracket notation (obj[key]), even when the exact property names aren't known in advance. entries. But, at Oct 27, 2023 · How can I access a dynamic object key? Should I pass a generic type for validation? I'm seeking a simple solution similar to plain JavaScript, allowing for one-line access with a null fallback when the key doesn't exist. defineProperty without manually defining them. These names are essential for defining the shape of objects and specifying the keys used to access values within them. You can set properties on the interface that point to nested objects. Aug 8, 2022 · I'm new to TypeScript and I'm trying to port some of my custom components/plugins to TS. This feature enables developers to write more flexible and dynamic code that can adapt to various scenarios. In this article, we'll delve into the world of dynamic keys in TypeScript and explore how you can use them effectively. I'll show you how they work in this article. entries Asked 5 years ago Modified 1 year, 1 month ago Viewed 18k times Any of these things can be used to construct different caches. One of the things I just can't seem to get right is setting (typed) object properties dynamically (i. Jun 20, 2025 · Learn how to dynamically access object properties by string in TypeScript with real-world examples, perfect for handling dynamic forms and API data. foo Jan 5, 2022 · Unless you're going to make the function generic, it would be something like {[k: string]: () => true}. Nov 12, 2020 · I need to access the properties of my object dynamically using a given string as the key. Typescript: bracket notation property access Asked 9 years, 8 months ago Modified 6 years, 6 months ago Viewed 98k times Aug 19, 2020 · Sorry if this has been asked/answered previously but I am trying to find how - if possible - to properly use features of TypeScript to dynamically read from properties of an object. Oct 14, 2023 · In TypeScript, leverage type safety to ensure that dynamic key access is valid and aligns with the defined types of the object and its properties. May 2, 2017 · This is just a convention in TypeScript, available for convenience. Oct 1, 2024 · Dynamically assign properties to TypeScript objects using the Record and Partial utility types, optional object properties, and more. using the string x, I would like to get string type and using the string y I want to get number type. Learn how to effectively use string interpolation in Angular and TypeScript to access variable properties dynamically. , you can use this operator to access properties of an object, where the o Jun 15, 2025 · In TypeScript, accessing an object's property using a key is a fundamental operation. ) to get access or modify an object property. However typescript seems to How to access object property with dynamic key in Typescript? Asked 3 years, 8 months ago Modified 3 years, 8 months ago Viewed 4k times Following is an ES6 example of how you can access the property of an object using a property name that has been dynamically generated by concatenating two strings. The access pattern is the same for each endpoint and you want to keep your code DRY. Mar 9, 2019 · you can use js es6 destructuring like: create an object that property name like variables and assign values to the properties, is more clean than you loop in array. ---This video is based on the questio Aug 25, 2020 · Typescript - Update object properties dynamically with Object. My code: interface Options { repeat: boolean; Feb 17, 2023 · By Dillion Megida When declaring objects before ES6, you had to use static keys for properties. I have a generic type that take a type in parameter. Inside another object I need to call that dynamic property's value, but because Oct 1, 2024 · In TypeScript, Objects are the fundamental data structures that use key-value pair structures to store the data efficiently. Works great, I just can't get it to play nicely with Typescript. There is no dynamic typing going on; even if you use a generic type parameter, Typescript is a statically typed language and the types don't even exist at runtime. You're writing an integration against a web API. TypeScript offers special syntax for turning a constructor parameter into a class property with the same name and value. We would like to show you a description here but the site won’t allow us. create () method You can use a square bracket [] or dot notation (. The least verbose way of doing this is to use the && operator. string. Upvoting indicates when questions and answers are useful. I can throw anything in there. The accessor function takes an object and returns the value of the property Sep 13, 2022 · Solution 2: Use an object index signature Solution 3: Use the Record utility type Understanding the problem with dynamically assigning properties to objects Generally speaking, TypeScript determines the type of a variable when it is declared, and this determined type doesn’t change, i. Understanding Index Signatures in TypeScript Index signatures in TypeScript provide a powerful way to define types for objects with dynamic property names while maintaining type safety. Combining generics with other TypeScript features, such as interfaces and type aliases, you can create powerful, flexible, and maintainable typings for any situation, especially for complex data structures like deeply nested objects. This is indeed a tricky problem because TypeScript 's type system is static, and it doesn't inherently understand runtime modifications like Object. If you want to access some arbitrary property that is not defined in the type signature of the object, you can use the ["foo"] notation, and the type checker will not try to enforce that the instance you're accessing has such a property in its type signature. Master index signatures in TypeScript to handle dynamic properties and create flexible, type-safe objects 🚀 Oct 10, 2019 · I need to dynamically access to object property in forEach. What are Static and Dynamic Keys? What do I mean by Jan 27, 2022 · That tells TypeScript that if that function doesn't throw, the key passed in is a valid key for FrcCapacity objects. Jan 7, 2024 · Here, ProfileType is an object type with name and age, and ProfileNameType is a string type, accessed via two levels of property names. These are called parameter properties and are created by prefixing a constructor argument with one of the visibility modifiers public, private, protected, or readonly. Dec 8, 2016 · I want to assign properties to the instance of a class without knowing the property names, values and types of values in TypeScript. ts script: // This co Dec 14, 2024 · In Typescript, property names refer to the identifiers used to access and manipulate the properties of an object. But since the release of ES6, you can use dynamic keys. Nov 16, 2020 · I need to access an object property in Typescript for which two levels are dynamic, e. But if you use useState<keyof typeof cities>("ny"); that will pick up that it's not just a string but specific string in an object ("ny" and "ld" in this case). Obviously, it's less than ideal that you have to repeat all the property names, but there we are. May 2, 2024 · In TypeScript, we can not assign the properties dynamically to an object directly by using the dot operator and the square brackets syntax which we generally use to assign dynamic properties in Vanilla JavaScript. Here’s how you could implement this with keyof: Nov 9, 2019 · TypeScript 3. Sep 16, 2023 · Indexed Access Types are a valuable tool in TypeScript for working with complex data structures, objects with dynamic keys, and arrays of objects. Jun 28, 2022 · typescript strict mode dynamically access different properties of different objects Asked 2 years, 8 months ago Modified 2 years, 8 months ago Viewed 381 times Mar 3, 2023 · typescript dynamically access object property Add Answer Tender Turtle answered on March 3, 2023 Popularity 6/10 Helpfulness 5/10 When working with TypeScript, accessing object properties dynamically by string can be a powerful technique. By defining index signatures in interfaces, you can create flexible data structures that enable dynamic property access. You may use any or unknown if they may have any value. The following code w TypeScript index signatures define dynamic object properties with type safety, allowing flexible key-value structures like dictionaries and configurations. Indexed Access with Arrays Like objects, TypeScript also allows indexed access types with arrays and tuples, which is great for ensuring type safety in list structures. This can be done using Dot Notation, Bracket Notation, and Optional Chaining. These are the following May 2, 2019 · How to access a property of an object using the bracket notation in TypeScript strict mode Asked 6 years, 3 months ago Modified 3 years, 3 months ago Viewed 13k times Mar 1, 2025 · You want to automatically infer and add types for all properties dynamically added via Object. Jul 9, 2024 · Enums are a feature in TypeScript that help organize collections of related values. Basic JavaScript: Accessing Object Properties with Variables, the second example (see below). There are two ways to achieve this. Hence, you can write code such as: const value = a?. This helps catch potential errors during development and provides better code completion and IDE support. This approach enables dynamic typing while ensuring type safety. javascript reactjs typescript edited Oct 28, 2023 at 3:32 James Olinya 17725 asked Oct 27, 2023 at 2:39 Angga Ari Wijaya 1 Nov 23, 2021 · You can't use string type to access properties on your object without index type. readonly Properties Properties can also be marked as readonly for TypeScript. With index types, you can get the compiler to check code that uses dynamic property names. Accessing these values efficiently is crucial for clean, maintainable code. TypeScript is a superset of JavaScript and provides several ways to iterate over object properties. I can be like a 1 or a number, etc. E. Conclusion By utilizing generics and the keyof keyword in TypeScript, you can easily access dynamic object properties while keeping the type information intact. Sep 3, 2024 · TypeScript's Indexed Access Types allow you to access the type of a specific property within an object or array using bracket notation (Type [Key]). Nov 4, 2024 · Attempting to access properties on such objects without checking for nullability can lead to errors. Jun 18, 2020 · When you try to access an object's property, you need to use a type keyof. In this tutorial, we will explore various techniques and examples of working with dynamic object keys in TypeScript. Dec 14, 2024 · Conclusion In conclusion, TypeScript object key indexing is a powerful feature that allows you to access object properties dynamically using keys. They allow you to extract the types of specific properties, improving type safety and code readability. In TypeScript, accessing object properties dynamically by using variables can be a common requirement when dealing with dynamic data or configurations. Mapping Dynamic Object Keys in TypeScript Dynamic property maps are a super powerful paradigm in JavaScript, but they can be tricky to type correctly with TypeScript. g. Oct 14, 2023 · Can I Add or Remove Properties from a TypeScript Object Dynamically? In TypeScript, once you define the type of an object, you cannot add or remove properties from it dynamically. TypeScript then knows you are not assigning a random string; you are assigning strings compatible with the properties (keys) for the object. Oct 21, 2024 · Should it be dynamic and update automatically if ParentObject changes? Should it be dynamic and update automatically if the actual object changes? Right now I've got this playground link but I made some assumptions about what the minimal reproducible example looks like and what your goal is. Jun 13, 2025 · Learn how to conditionally add properties to objects in TypeScript using if statements, spread operator, and utility type like Partial with real world examples. Jun 15, 2015 · Is there any way to define a dynamic object type in TypeScript? In the following example, I would like to define a type for "My Complex Type" by saying: Objects of type "My Complex Type" are obje TypeScript is a language for application-scale JavaScript development. In TypeScript you can't dynamically add a property to an object containing properties with different types--unless you cast to any (which, in my opinion, should be avoided). Feb 2, 2017 · You'll need to complete a few actions and gain 15 reputation points before being able to upvote. This flexibility opens up a wide range of possibilities for handling data in a more dynamic and efficient manner. we are going to explore multiple approaches to achieve this. hxlhx nbcxo odpq llzbh wqkmr keh ldixzjm iygd ani tzeq