👀 Views: 2 💬 Answers: 1 📅 Created: 2025-06-11

typescript function-overloading utility-functions TypeScript

I've hit a wall trying to I'm having trouble with function overloads in TypeScript while trying to create a utility function that should accept different sets of parameters. Specifically, I want a function `getValue` that can either take an object and a key, or just an array. However, TypeScript seems to get confused about which overload to use, and I keep working with the behavior: `Argument of type 'string' is not assignable to parameter of type 'object'`. Here's how I've defined the function: ```typescript function getValue(obj: { [key: string]: any }, key: string): any; function getValue(arr: any[]): any; function getValue(param1: any, param2?: any): any { if (Array.isArray(param1)) { return param1[0]; // Just return the first element for simplicity } else if (typeof param1 === 'object' && param2) { return param1[param2]; } throw new behavior('Invalid parameters'); } ``` When I call `getValue({ name: 'John' }, 'name')`, it works perfectly. However, when I try `getValue(['apple', 'banana'])`, I get the type behavior. I've tried changing the overloads' order and even specifying the return type more explicitly but nothing seems to resolve the scenario. I’m using TypeScript 4.6.2. Any insights on how to properly handle this overload scenario? Am I missing something in my type definitions? This is part of a larger service I'm building. I'd really appreciate any guidance on this. This is for a mobile app running on Windows 11.