完善自定义 Hook —— useArray ,使其能够完成 tryUseArray 组件中测试的功能:
相关文件代码:
import { useEffect, useState } from "react";
export const useMount = (cbk: () => void) => useEffect(() => cbk(), []);
export const useArray = () => {};
import { useArray, useMount } from "utils";
const TryUseArray = () => {
const persons: { name: string; age: number }[] = [
{ name: "jack", age: 25 },
{ name: "ma", age: 22 },
];
const { value, clear, removeIndex, add } = useArray(persons);
useMount(() => {
// 期待这里报错:Property 'notExist' does not exist on type '{ name: string; age: number; }[]'.
// console.log(value.notExist);
// 期待这里报错:Property 'age' is missing in type '{ name: string; }' but required in type '{ name: string; age: number; }'.
// add({ name: "david" });
// 期待这里报错:Argument of type 'string' is not assignable to parameter of type 'number'.
// removeIndex("123");
});
return (
<div>
{/*期待: 点击以后增加 john */}
<button onClick={() => add({ name: "john", age: 22 })}>add john</button>
{/*期待: 点击以后删除第一项*/}
<button onClick={() => removeIndex(0)}>remove 0</button>
{/*期待:点击以后清空列表*/}
<button style={{ marginBottom: "50px" }} onClick={() => clear()}>
clear
</button>
{value.map((person, index) => (
<div key={index} style={{ marginBottom: "30px" }}>
<span style={{ color: "red" }}>{index}</span>
<span>{person.name}</span>
<span>{person.age}</span>
</div>
))}
</div>
);
};
export default TryUseArray;
import "./App.css";
import TryUseArray from "tryUseArray";
function App() {
return (
<div className="App">
<TryUseArray />
</div>
);
}
export default App;
答 答 答
案 案 案
在 在 在
后 后 后
面 面 面
, , ,
没 没 没
有 有 有
完 完 完
成 成 成
不 不 不
要 要 要
偷 偷 偷
看 看 看
哦 哦 哦
! ! !
import { useEffect, useState } from "react";
// 我的练习作业
// export const useArray = (array: T[]) => {
// const [value, setValue] = useState(array)
// const clear = () => setValue([])
// const removeIndex = (index: number) => setValue([...value].filter((item, _index) => _index !== index))
// const add = (item: item) => setValue([...value, item]))
// return {
// value, clear, removeIndex, add
// }
// }
export const useArray = <T>(array: T[]) => {
const [value, setValue] = useState(array);
return {
value,
add: (item: T) => setValue([...value, item]),
removeIndex: (index: number) => {
const temp = [...value];
temp.splice(index, 1);
setValue(temp);
},
clear: () => setValue([]),
};
};
官方文档:自定义 Hook – React
js/ts
函数中不可用)
- Hook 规则 – React
export const useMount = (cbk: () => void) => useEffect(() => cbk(), []);
import { useMount } from "utils";
const [list, setList] = useState([]);
useMount(() => {
fetch(`${apiUrl}/list`).then(async (res) => {
if (res.ok) {
setList(await res.json());
}
});
});
/**
* @param { 值 } val
* @param { 延时:默认 1000 } delay
* @returns 在某段时间内多次变动后最终拿到的值(delay 延迟的是存储在队列中的上一次变化)
*/
export const useDebounce = <V>(val: V, delay: number = 1000) => {
const [tempVal, setTempVal] = useState(val);
useEffect(() => {
// 每次在 val 变化后,设置一个定时器
const timeout = setTimeout(() => setTempVal(val), delay);
// 每次在上一个 useEffect 处理完以后再运行(useEffect 的天然功能即是在运行结束的 return 函数中清除上一个(同一) useEffect)
return () => clearTimeout(timeout);
}, [val, delay]);
return tempVal;
};
import { useDebounce } from "utils";
// 对 param 进行防抖处理
const lastParam = useDebounce(param);
const [list, setList] = useState([]);
useEffect(() => {
fetch(
// name=${param.name}&personId=${param.personId}
`${apiUrl}/projects?${qs.stringify(lastParam)}`
).then(async (res) => {
if (res.ok) {
setList(await res.json());
}
});
}, [lastParam]);
注意区别于 节流
拓展学习:
- 【笔记】Custom Hook
官方文档:
- TypeScript: Documentation - Generics
- 泛型(generic) - TypeScript 中文手册
拓展学习:
- 【笔记】TS 泛型