👀 Views: 1468 💬 Answers: 1 📅 Created: 2025-06-21

typescript function-overloading validation

I'm trying to implement I'm trying to debug I'm working on a project and hit a roadblock. I'm updating my dependencies and I'm converting an old project and I'm stuck on something that should probably be simple. After trying multiple solutions online, I still can't figure this out. I'm working with a question while trying to implement a validation utility in TypeScript that uses function overloads for handling different types of inputs. I have a utility function that should validate either a string or an array of strings, but I'm running into issues with type inference and overload resolution. Here's the code I have so far: ```typescript function validateInput(input: string): boolean; function validateInput(input: string[]): boolean; function validateInput(input: any): boolean { if (typeof input === 'string') { return input.length > 0; } else if (Array.isArray(input)) { return input.every(item => typeof item === 'string' && item.length > 0); } return false; } ``` When I call `validateInput('')`, it returns `false` as expected. However, when I call `validateInput(['valid', ''])`, I get an unexpected behavior where it returns `true` instead of `false`. The scenario seems to arise from the way I'm checking the conditions inside the function. I've tried adjusting the checks to ensure each item in the array is validated correctly, but I still encounter the same question. Here's the call that causes confusion: ```typescript const result = validateInput(['valid', '']); // Expected: false, Got: true ``` I've also considered using a more explicit type guard, but I'm not sure how to implement that effectively. Any suggestions on how to ensure the function correctly validates both strings and arrays of strings, especially when it comes to handling empty strings in an array? Also, should I be handling cases where the input might not be a string or an array at all? I'm using TypeScript 4.5.4 for this project, and I've ensured that my strict mode is enabled. I'm working on a web app that needs to handle this. Any ideas what could be causing this? The stack includes Typescript and several other technologies. Is there a better approach? Any help would be greatly appreciated! This is happening in both development and production on Debian. For reference, this is a production web app. Hoping someone can shed some light on this.