Implement a useCounter hook that manages a counter state, with some additional convenience utility methods.
export default function Component() {const { count, increment, decrement, reset, setCount } = useCounter();return (<div><p>Counter: {count}</p><button onClick={increment}>Increment</button><button onClick={decrement}>Decrement</button><button onClick={reset}>Reset</button></div>);}
initialValue: number: Initial value of the counter state. If not provided, it should default to 0.The useCounter hook returns an object with the following properties:
count: number: The current counter valueincrement: () => void: A function to increment the counter valuedecrement: () => void: A function to decrement the counter valuereset: () => void: A function to reset the counter value to initialValue, or 0 if not providedsetCount: (value: number) => void: A function to set the counter value to value, it has the same signature as setStateImplement a useCounter hook that manages a counter state, with some additional convenience utility methods.
export default function Component() {const { count, increment, decrement, reset, setCount } = useCounter();return (<div><p>Counter: {count}</p><button onClick={increment}>Increment</button><button onClick={decrement}>Decrement</button><button onClick={reset}>Reset</button></div>);}
initialValue: number: Initial value of the counter state. If not provided, it should default to 0.The useCounter hook returns an object with the following properties:
count: number: The current counter valueincrement: () => void: A function to increment the counter valuedecrement: () => void: A function to decrement the counter valuereset: () => void: A function to reset the counter value to initialValue, or 0 if not providedsetCount: (value: number) => void: A function to set the counter value to value, it has the same signature as setStateThe useCounter hook uses useState to manage the number state. The setter functions can be implemented in terms of setValue from the useState hook.
import { useState } from 'react';export default function useCounter(initialValue = 0) {const [count, setCount] = useState(initialValue);return {count,increment: () => setCount((x) => x + 1),decrement: () => setCount((x) => x - 1),reset: () => setCount(initialValue),setCount,};}
To ensure consistency, the increment and decrement functions use an updater function to calculate the new value based on the previous value.
If you're using TypeScript, the tricky part is figuring out the right type for setCount since it can also accept an updater function. Simply hover the setter function from useState in your favourite IDE and you'll see the type signature in the form of Dispatch<SetStateAction<...>> where the type of the state is .... Dispatch and SetStateAction can be imported from react.
If you prefer to be verbose, it essentially boils down to this.
type SetCount = (valueOrUpdater: number | ((previousValue: number) => number),) => void;
console.log() 语句将显示在此处。