我试图让我的搜索栏显示一些结果,但它没有,并且显示错误
Cannot read properties of null (reading 'map')
// import axios from "axios";
import React, { useEffect, useState } from "react";
import lodu from "../../utils/lodu"
import { Link } from "react-router-dom";
function Topnav() {
const [query, setquery] = useState("");
const [searches, setsearches] = useState(null);
const getSearches = async () => {
try {
const { data } = await lodu.get(`/search/multi?query=${query}`);
setsearches(data.results)
} catch (error) {
console.log("error is ", error)
}
}
useEffect(() => {
getSearches();
}, [query])
return (
<>
<div className="w-full h-[12vh] relative flex justify-center items-center">
<i class="text-zinc-400 text-3xl ri-search-2-line"></i>
<input onChange={(e) => { setquery(e.target.value) }} value={query} className="w-[50%] text-zinc-200 mx-10 p-3 text-xl outline-none bg-transparent border-none" type="text" placeholder="search anything?" />
{query.length > 0 && (<i
onClick={() => setquery("")}
class="text-zinc-400 text-3xl ri-xrp-fill"></i>)}
<div className="w-[50%] absolute max-h-[50vh] bg-zinc-200 top-[90%] overflow-auto">
{searches.map((s, i) => (
<Link key={i}
className="hover:text-zinc-100 hover:bg-zinc-400 duration-200 font-semibold w-[100%] flex justify-start items-center p-8 bg-zinc-200 border-b-2">
<img src="" alt="" />
<span>hi</span>
</Link>
)
)}
</div>
</div>
</>)
}
export default Topnav
页面加载搜索设置为空。另外,在页面加载时,您正在映射搜索。
尝试将
{searches.map((s,i)=>{
更改为 {searches?.map((s,i)=>{
将
useState
默认值更新为空数组。
const[searches,setsearches]=useState([]);
您可以简单地添加检查搜索结果是否具有某些值,然后仅像这样映射:
{searches && searches.length > 0 && searches.map((s, i) => (
<Link key={i}
className="hover:text-zinc-100 hover:bg-zinc-400 duration-200 font-semibold w-[100%] flex justify-start items-center p-8 bg-zinc-200 border-b-2">
<img src="" alt="" />
<span>hi</span>
</Link>
)
)}
并更新搜索的默认值如下:
const [searches, setsearches] = useState([]);
最初,您已将搜索状态变量的值设置为空:
const[searches,setsearches]=useState(null);
然后立即在 null 上调用 map 方法
{null.map((s,i)=>{
return (<Link key={i}
className="hover:text-zinc-100 hover:bg-zinc-400 duration-200 font-semibold w-[100%] flex justify-start items-center p-8 bg-zinc-200 border-b-2">
<img src="" alt="" />
<span>hi</span>
</Link>)
})}
这会生成错误“无法读取 null 的属性(读取“地图”)”。要解决此问题,请将搜索的初始值设置为空数组,以便映射方法成为数组上的有效方法调用(无论是否为空)。
const[searches,setsearches]=useState([]);
或者在对“searches”变量调用“map”方法之前检查它是否已使用“Async”函数“getSearches”返回的数据进行更新:
{searches && searches.map((s,i)=>{
return (<Link key={i}
className="hover:text-zinc-100 hover:bg-zinc-400 duration-200 font-semibold w-[100%] flex justify-start items-center p-8 bg-zinc-200 border-b-2">
<img src="" alt="" />
<span>hi</span>
</Link>)
})}