Typescript spread operator missing properties. The star of the show in optional chaining is the new ?.
Typescript spread operator missing properties For example interface Foo {a: number; b: string} suggests something with type Foo has an a and b property. We spent a lot of time implementing some Nov 2, 2015 · Original answer: This seems to be a typescript ES6 transpilation quirk . 1 documentation. The operator should work on anything that has an iterator property, (Accessed by obj[Symbol. Object. Jan 6, 2023 · In TypeScript, you can dynamically assign properties to an object using various approaches. Conclusion Dealing with missing properties in TypeScript can be challenging, but with elegant solutions like using the spread operator, you can ensure that your objects maintain their structure Jan 31, 2020 · The second modifiedTodos2 line of code gives me the following error: property date is missing in type [] In my scenario, I'm required to use the spread operator to extend the todo object with an additional prop. You can work with rest/spread properties in a type-safe manner and downlevel both features to ES3. If Foo defined any methods, for instance Jan 20, 2023 · Note that when using the spread operator to merge 2 or more objects, if they happen to have common properties, the one from the last spread object will be used as source of truth: Mar 13, 2019 · React with Typescript - Type { } is missing the following properties from type Asked 6 years, 8 months ago Modified 2 years, 9 months ago Viewed 280k times 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. me/x9l9ctn9wz/1 May 8, 2024 · Object spreading in TypeScript refers to spreading the properties of an object into another object or function call. . My second guess is that drawInfo has optional properties and the evaluator is seeing the possibility that the spread would result in 0 params. js, showcasing practical examples of copying arrays, merging objects, and spreading function arguments. const person = { name: 'Alice', age: 30 }; Jan 7, 2025 · In conclusion, mastering TypeScript's spread operator with array indexes can significantly simplify your code and improve its readability. js const transformedResponse = transformResponse(response); const Jul 22, 2013 · I think the spread is more clear, but it's a huge difference for larger objects in code that could easily be on a bottleneck (eg delaying rendering data returned from fetch), so I'd recommend adding a comment explaining the comma operator use. Apr 10, 2020 · It's a minor detail, but technically this isn't the "spread" operator, it's the "rest" operator when you use it in destructuring. Feb 12, 2022 · 2 Extract Values from an object 3 Exclude Values from an object with Rest Operator Spread Operator vs Rest Operator in Typescript and Javascript The Spread Operator The Rest Operator Bonus: Another way to clone an object 4 Combine objects with Spread Operator Combine Multiple Objects Combine objects with different properties 5 Change Multiple Mar 30, 2024 · This comprehensive guide delves into the spread operator, a powerful tool in JavaScript and TypeScript. This is achieved using the spread operator. The guide then explores its usage in Node. I'm trying to define a type which gets a function type as a generic parameter and returns a function type which is the same as the input function type except it has one more argument at the end: Apr 6, 2023 · Generic spread in TS results in an intersection, which is often a reasonable approximation but when you overwrite properties then it's not great. If you're not familiar with spread, it essentially turns an object, or anything that is iterable into separate elements. Type guarding properties only narrows the parent if the parent is of a discriminated union type, which TotoInt isn't (fixed to adhere to standard TS naming conventions). Dec 9, 2016 · A new feature since TypeScript 2. iterator]) and Sets have that property. Dec 3, 2023 · This quick article shows you 2 different approaches to merging 2 or more objects in TypeScript. Dec 31, 2018 · How in TypeScript without untyped unsafe crutches (<>, as, any, unknown and similar) can one exclude fields in object spread (so without enumerating every field I want to copy)? Jun 21, 2019 · This is related to #10727 and #28234 about how we don't have a real spread type and tend to use intersections in generic cases and Object. Feb 14, 2018 · So firstly, Object Rest/Spread is a proposed ECMAScript feature that is well on its way to being standardized, having reached Stage 4, and is in the process of being formally adopted. May 15, 2019 · I want to delete drugName from the response but it is not happening any idea how to delete property from spread operator ? main. Using the spread operator There are some important things Dec 9, 2015 · I think @Fenton explains it very well but I would like to add some more documentation and possible solutions. Nov 21, 2018 · How to remove an object's property when using the spread syntax in order to create a new instance of an object? Ops example used the keyword public for his constructor argument, which acts as a declared property. It's used to expand an array or object into individual elements or properties. Mar 26, 2018 · 104 I have a function that adds a key to incoming object, but I have been told to use the spread operator for that, I have been told that I can use the spread operator to create a new object with the same properties and then set isAvailable on it. Double-check the version in the bottom right of your IDE window. I am expecting a solution for using typescript constructor with spread operator. I was trying to manipulate an object and remove one of the properties but I didn’t want to mutate the original object. How to enforce TypeScript to do the checking? Jun 13, 2019 · Now i want to add a property to inner object "type". Learn how to leverage it for seamless prop passing, enhancing your React development experience. This can come in handy when you need to make a copy of an existing object or array, or when you want to merge multiple array s or objects together. This article explains the spread operator in TypeScript and shows many code examples. Jul 6, 2025 · Learn how to use the TypeScript spread operator to manipulate arrays and objects, create copies without mutation, and leverage TypeScript's type safety in your projects. Jan 7, 2025 · The spread operator is a powerful tool in TypeScript, but it's essential to understand its limitations and potential pitfalls. As of TypeScript 3. jobTitle was null, it wouldn't be included in data, thus protecting us from the dreaded 400 errors. If I'm wrong about that, I'll need to see your drawInfo object definition. They’re also values, and just like other values, TypeScript has many ways to describe how functions can be called. What are TypeScript Spread Operators? The spread operator in TypeScript is denoted by three dots (). assign work but not the spread operator. Dynamically adding properties allows you to create flexible and extensible data structures based on runtime conditions or user input. This innovative use of the spread operator and conditional rendering allowed the code to elegantly handle optional properties, eliminating unexpected errors. Remember that it is shallow copy, it means that if object is nested then its nested composite params will exists in the new object by the same reference. Jan 10, 2016 · @wensveen Spreading the result like that is incredibly slow, and even if you do it properly filter+reduce is still slower than just reduce, and both are slower than Object. create(proto), attributes) Essentially my question is why does Object. Jun 5, 2022 · How to exclude one key/value pair from spread operator return [duplicate] Asked 3 years, 5 months ago Modified 3 years, 5 months ago Viewed 16k times Apr 1, 2021 · I have tried to read how to delete a property from an object in here: How do I remove a property from a JavaScript object? it should use delete, I try it like this const eventData = {myEvent}; // Feb 25, 2023 · An alternative might be to overwrite the property you don't want, i. from(new Set([1, 2, 3, 1, 1])). To work around this, you can use Array. This article will cover advanced ways to use the spread operator, common issues, and solutions. An simple example would be this: interface Car { name: st Oct 19, 2025 · The TypeScript spread operator, combined with object destructuring, provides a simple and elegant way to exclude properties from an object. Refer to the TypeScript 3. I want to to this with the spread syntax, since i need a new object, because the existing is an immutable state object. Feb 13, 2022 · Is there anyway to use spread clone AND keep readonly No. 7 (released on November 5, 2019), this feature is supported and is called Optional Chaining: At its core, optional chaining lets us write code where TypeScript can immediately stop running some expressions if we run into a null or undefined. Similarly, . Moving on to TypeScript, it Jan 26, 2015 · Spread operator takes all fields from obj1 and spread them over obj2. This mainly Jun 30, 2025 · Learn how to merge objects in TypeScript, including deep merge, spread operator, Object. How to use object spread with nested properties? Asked 8 years ago Modified 3 years, 4 months ago Viewed 56k times Learn how to dynamically assign properties to an object in TypeScript with this helpful guide. Does that fully address May 8, 2019 · Need to assign porperties to the only defined from the interface if used with spread operator. Spread Operator The main objective of the spread operator is to spread the elements of an array or object. Feb 13, 2022 · TS2740: Missing properties from type when using spread operator Asked 3 years, 9 months ago Modified 3 years, 9 months ago Viewed 2k times Jul 23, 2025 · The spread operator in TypeScript simplifies array and object manipulation by enabling easy copying, combining, and property modification. iterator)). Information about the typing of the feature is available in the TypeScript 2. In this blog post, we will explore the fundamental concepts of the TypeScript spread operator, its usage methods, common practices, and best practices. May 5, 2016 · Use Typescript spread operator it transpile to Javascript Object. The type of the final object will successfully be inferred. assign() Feb 2, 2024 · Use the Spread Operator to Clone Objects in TypeScript The spread operator is a new addition to the features available in the JavaScript ES6 version and can make effective copies of an object. apply: function foo(x, y, z) { } var args = [0, 1, 2]; foo. I prefer this solution in this case because it keeps some kind of type safety and avoids ignore and any. As a result, we now need to spell out each property explicitly and never use the spread operator. Jan 21, 2021 · This works and compiles, assuming that ApiDTO has the right types. Here's the setup: Interface to define my types: interface Jan 17, 2017 · Yes. Feb 16, 2024 · I have a issue that when using a spread operator in Typescript the compiler won't complain that the property you change does not exist. Dec 16, 2022 · The spread operator —spoiler alert— can spread the contents of an array or an object. As you know from its usage, it makes working with plain JavaScript objects, incredibly flexible. The original method and function call does not need to be rewritten at all. assign(Object. In this article, we'll dive deep into the world of spreading properties, arrays, and more, helping you master the art of using the spread operator on objects in TypeScript. assign+delete if the object has more than 20 properties: jsbench. Shallow-cloning (excluding prototype) or merging of objects is now possible using a shorter syntax than Object. The spread operator seems to assume that an undefined optional property is missing and will not overwrite previously set properties. Feb 6, 2024 · In TypeScript, you can merge two objects by using the spread operator … to combine the properties of both objects into a new one. What is the spread operator? The spread operator (…) expands any iterable object into a list of arguments. It simplifies complex operations like copying, merging, and passing multiple arguments, making your code more Jan 7, 2025 · When it comes to working with objects in TypeScript, the spread operator is a powerful tool that can simplify your code and make it more efficient. Derived from JavaScript, the spread operator allows you to expand iterable objects such as arrays, strings, and objects. assign, or type assertions, TypeScript offers flexible solutions to handle this common scenario effectively. However, when spreading objects that may have missing properties, TypeScript's type system can sometimes present challenges. Without a built in spread type operator as requested in ms/TS#10727, this is just how it is. Solutions: Function overload. By following best practices and exploring real-world examples, you'll become proficient in using this powerful feature to enhance your coding skills. Understanding Object Spread in TypeScript Object spread syntax in TypeScript allows you to create a new object by copying the properties from an existing object. assign, lodash, and utility types with the help of real time examples. Spread Operator The main objective of the spread operator is to spread the objects of an array. operator for optional property accesses. Functions are the basic building block of any application, whether they’re local functions, imported from another module, or methods on a class. It is a valuable tool for data sanitization, API response manipulation, and maintaining type safety. This assumption is probably correct most of the time, but not in the example here. There's nothing you can add to your class to change that behavior. Without any further ado, let’s get our hands dirty by writing some code. assign(), but that spread expressions with known concrete class instance only preserve non-method properties. Apply A common use case is to spread an array into the function arguments. Feb 27, 2024 · Use the spread syntax () to merge objects in TypeScript. Feb 27, 2023 · The spread operator allows to spread or expand iterable objects into individual elements. When working with objects that may have missing properties, using the Partial type can help prevent unexpected behavior and ensure that your code is robust and maintainable. Oct 26, 2017 · Come to think of it, I guess it makes sense that Object literal spread syntax doesn't fail, since what it's spreading is often another plain object, and those aren't Iterators by default, so they almost have to make an exception in that case. This rule disallows using the spread syntax on values whose types indicate doing so may cause unexpected behavior. Jun 8, 2023 · If payload. lastName are missing in all getter methods, because at runtime this in these contexts refers to an empty object { isJohn: [Getter], isDoe: [Getter] }, not the object containing the spread properties. Its concise syntax enhances code readability and efficiency, making it an essential tool for modern TypeScript development. 7 Aug 20, 2018 · Search Terms: spread operator, property getter Code interface IWhatever { readonly value: number; } class Whatever implements IWhatever { public get value() { return 42; } } const whatever: IWhatev TypeScript allows spreading objects whose properties are not typically meant to be enumerated, such as arrays and class instances. Oct 19, 2025 · In TypeScript, the spread operator (``) is a powerful and versatile syntax feature that has significantly enhanced the way developers write and manage code. Jul 21, 2017 · Vscode may be using a version of typescript before 2. I knew there must be a cleaner way than to use the delete operator. Function Type Expressions The simplest way to describe a function is Mar 13, 2023 · If we compose an object by spreading 2 different types of objects, then TypeScript does not do the type-checking. Jul 23, 2025 · The spread operator in TypeScript simplifies array and object manipulation by enabling easy copying, combining, and property modification. userData will still have a token property but it will be undefined. Oct 17, 2022 · const extendedarray = dataArray. Considering the example in the previous code segment. In the result you get new object with new reference and the same fields as original one. The result of { foo } is a plain object with read/write public data properties for the own, enumerable properties of foo. See ms/TS#50559 and the issues it links to. Let’s learn about how to write types that describe functions. from to convert the set to an array first: Array. Jul 30, 2018 · [The spread operator] copies own enumerable properties from a provided object onto a new object. EDIT: drawInfo appears to be an Sep 21, 2022 · This is unfortunately a missing feature of TypeScript, see microsoft/TypeScript#42384. The star of the show in optional chaining is the new ?. assign () to achieve the same result. const userData = { data, token: undefined }. apply(null, args); Now you can do this simply by prefixing the arguments Discover the power of the spread operator in React. Alternatively, you can use Object. If the spread operator would work like he wants, then all properties would be declared. firstName and this. By using it, you can take elements from arrays or properties from objects and spread them into a new array or object. Oct 10, 2025 · TypeScript should consistently report that both this. The "better" way is probably to try to emulate such an operator with Omit as shown here. It starts with an introduction to the spread operator, explaining its purpose and significance in modern programming. 1 to evaluate the code. It’s basically the opposite of destructuring. 1, object rest and spread allows you to make copies, merge and destructure objects. Previously you would need to use Function. How do you use spread operator to overwrite properties in typescript Asked 5 years, 4 months ago Modified 1 year, 5 months ago Viewed 18k times TypeScript Spread Operator The TypeScript spread operator () is a handy feature that can make your code simpler and easier to read. Whether you prefer the spread operator, Object. Also note that because { foo } creates a plain object, it will no longer be an instance of Foo. As it very eloquently Jul 20, 2025 · The spread () syntax allows an iterable, such as an array or string, to be expanded in places where zero or more arguments (for function calls) or elements (for array literals) are expected. In an object literal, the spread syntax enumerates the properties of an object and adds the key-value pairs to the object being created. assign(). Jan 26, 2024 · The easiest solution to merge objects in TypeScript or JavaScript is the spread syntax, or spread operator. prototype. May 4, 2024 · In TypeScript, there are powerful features like the spread operator, rest operator, and destructuring that can significantly enhance your code’s readability and maintainability. Jan 12, 2019 · If I replace the spread with the following it works: return Object. However, if the API delivers any additional field, Prisma will throw at runtime, despite having all the relevant data. Oct 19, 2025 · The spread operator simplifies many common programming tasks, such as combining arrays, cloning objects, and handling function arguments. I'm trying to be cute with TypeScript and arrays and use the spread operator to essentially prepend an object to an array of objects. When used with objects, the spread operator creates a shallow copy of the object, maintaining the original properties while allowing you to add or override specific properties. It provides a concise way to merge objects or create copies with modified properties. That got me thinking about the spread operator and I remembered you can remove properties while spreading the rest of the values into a new object. assign is doing that the spread operator is missing? Jan 19, 2021 · The main problem is that TypeScript cannot guarantee in general that a type only has a given set of properties. assign () If you need deep tree object merging you could use changing function of best-global package Feb 27, 2023 · How to fix "Type ' { key: number; }' is missing the following properties" when sending props with spread operator in Next. create compiles if the DTO has all the required fields. A TypeScript operator performs tasks like assignment, comparison, and spreading values, letting you write cleaner, type-safe logic across your codebase. Sep 3, 2024 · Adding missing properties to objects in TypeScript is essential for maintaining code integrity and preventing runtime errors. Is there something Object. js App directory? Asked 1 year, 11 months ago Modified 1 year, 11 months ago Viewed 290 times Dec 23, 2016 · TypeScript 2. Feb 20, 2023 · The spread operator in TypeScript is a powerful feature that allows you to easily expand the contents of an array or object. map (x => {isSelected: false, x}) //Almost correct but was missing sone syntactic sugar! I've read this and many other answers but I can't figure it out : TypeScript add object to array with spread Nov 2, 2024 · Object Spread In addition to arrays, the spread operator can also be used with objects to merge or clone them. apply(null, args); Now you can do this simply by prefixing the Dec 19, 2017 · So, what is the actual difference between spreading into object vs array? When trying to spread into array, one gets Uncaught TypeError: boolean false is not iterable (cannot read property Symbol(Symbol. 1 adds support for object rest and spread. Think of it as a convenient way to "spread" an array or object across multiple places in your code. e. This is best explained with examples. ubhdwpvxewsdxgwpfnwirkszoajsqwjmjrbtbccwezjjpqoinkwysfiszisjmwdvmjbzoxzujhle