ProjectStack
typescript

TS2322: Type 'void' is not assignable to type 'X'

You're using the return value of a function that returns void — either by storing it in a variable, passing it to another function, or assigning it somewhere. Functions that return void produce no useful return value and the result cannot be used as data.

Common causes

  • Storing the result of a void-returning function: const result = array.forEach(...)
  • Passing a void-returning callback where a value-returning callback is expected
  • Chaining methods on a void result: arr.forEach() returns void, not the array
  • A function was changed to return void but its return value is still being used

How to fix it

  1. Don't capture the return value of void functions — just call without assignment
  2. Use a value-returning method instead: map() returns values, forEach() does not
  3. Restructure the code to not depend on the return value of the void function
  4. If the function should return a value, update its implementation and return type

Example

const result: string[] = ['a', 'b'].forEach(x => x.toUpperCase()); // error TS2322: Type 'void' is not assignable to type 'string[]'.

Assigning the result of forEach, which returns void, to a typed string[] variable

Related TypeScript Errors

Enum type mismatchType not assignable (TS2322)Property does not exist on type (TS2339)Argument not assignable to parameter (TS2345)Object is possibly null (TS2531)

Browse more errors

The Developer Hub covers 150+ errors across Git, npm, Node.js, Python, TypeScript, and Docker — with plain-English explanations and fix steps.