TypeScript Type Assertion scenarios with Dynamic Object Keys in React Component State Management
I keep running into I've been struggling with this for a few days now and could really use some help. I'm working on a project and hit a roadblock. I'm working on a React application using TypeScript, and I'm having trouble with type assertions when dynamically updating state. I have a state object that holds various properties, and I'm trying to update a specific property based on user input. However, TypeScript is throwing an behavior because it's unable to infer the correct type for the dynamic key. Here’s a simplified version of my code: ```typescript import React, { useState } from 'react'; interface MyState { name: string; age: number; email: string; } const MyComponent: React.FC = () => { const [state, setState] = useState<MyState>({ name: '', age: 0, email: '', }); const handleChange = (key: keyof MyState, value: string | number) => { setState(prevState => ({ ...prevState, [key]: value, })); }; return ( <div> <input type="text" onChange={e => handleChange('name', e.target.value)} /> <input type="number" onChange={e => handleChange('age', Number(e.target.value))} /> <input type="email" onChange={e => handleChange('email', e.target.value)} /> </div> ); }; ``` When I try to update the `age` property, TypeScript gives me the following behavior: `Type 'string' is not assignable to type 'number'.` This happens because I'm passing `e.target.value`, which is always a string, to the `handleChange` function without properly handling type coercion. I've tried creating a type guard to check the key and cast the value accordingly, but I’m still running into issues. Here’s what I attempted: ```typescript const handleChange = (key: keyof MyState, value: string | number) => { setState(prevState => ({ ...prevState, [key]: typeof value === 'number' ? value : value, })); }; ``` However, this doesn’t resolve the type scenario since the function signature does not enforce the type based on the key. Can anyone suggest a clean way to manage this or point out what I'm missing? I'm using TypeScript 4.5 and React 17.0.2. Thanks! What's the best practice here? My development environment is Ubuntu 22.04. Thanks, I really appreciate it! For reference, this is a production service. Any feedback is welcome! I'm using Typescript stable in this project. Is there a simpler solution I'm overlooking?