路由 (React Router)

1. Outlet

使用Layout模版的时候，中间的插槽使用<Outlet />

import { Outlet } from "react-router-dom";

2. createBrowserRouter() 来定义router的结构和格式

const router = createBrowserRouter([
  {
    path: "question",
    element: <QuestionLayout />,
    children: [
      {
        path: "edit/:id",
        element: <Edit />,
      },
      {
        path: "stat/:id",
        element: <Stat />,
      },
    ],
  },
  {
    path: "/",
    element: <MainLayout />,
    children: [
      {
        path: "/",
        element: <Home />,
      },
      {
        path: "/login",
        element: <Login />,
      },
      {
        path: "/register",
        element: <Register />,
      },
      {
        path: "manage",
        element: <ManageLayout />,
        children: [
          {
            path: "list",
            element: <List />,
          },
          {
            path: "star",
            element: <Star />,
          },
          {
            path: "trash",
            element: <Trash />,
          },
        ],
      },
      // 404 page
      {
        path: "*",
        element: <NotFound />,
      },
    ],
  },
]);

3. RouterProvider来配置好router

function App() {
  return <RouterProvider router={routerConfig}></RouterProvider>;
}

4. 页面跳转

方式1: useNavigate()

const nav = useNavigate();

nav("/login")

nav(-1)

nav({
      pathname: "/login",
      search: "b=21",
    });

获取参数

使用useParams()

如果路由里面定义为 "edit/:id"

获取这个id可以使用 useParams():

const { id = "" } = useParams();

如果是通过url传参数如 http://localhost:3000/manage/list?keyword=xxx

可以使用 useSearchParams()来获取

const [searchParams] = useSearchParams();
  console.log("keyword", searchParams.get("keyword"));

方式2: <Link to="/register">Register</Link>

Comments

Templates

Template - Polymorphism is the ability of the same code to operate on different types. This ability to operate on multiple types reduces code duplication by allowing the same piece of code to be reused across the different types it can operate on. - Polymorphism comes in a variety of forms. What we are interested in at the moment is parametric polymorphism, meaning that we can write our code so that it is parameterized over what type it operates on. -That is, we want to declare a type parameter T and replace int with T in the above code. -Then, when we want to call the function, we can specify the type for T and get the function we desire. C++ provides parametric polymorphism through templates. Templated Functions - We can write a templated function by using the keyword template followed by the template parameters in angle brackets (<>). - Unlike function parameters, template parameters may be types, which are specified with typename where the type of the parameter wo...

前端优化代码体积

当我使用npm run build的时候，项目构建了很久。所以考虑用create-react-app网站下面的工具来缩小代码体积 Analyzing the Bundle Size https://create-react-app.dev/docs/analyzing-the-bundle-size 更改完成后 npm run build npm run analyze 可以看到以下的图片: 其中main.js有1.57mb 然后起服务 serve -s build -l 8000 进入到首页之后，打开network，查看js，发现main.js有500kb。这个500kb是已经用gzip压缩过了，但是却还有这么大。500*3=1500说明源文件有1.5mb左右其中, antd占了25%, recharts占了13%, react-dom占了7.6%，dnd-kit占了2.8% 其中recharts用于统计页面，dnd-kit用于拖拽排序-编辑器页面。所以在加载首页的时候，先不加载编辑页面和统计页面的js的话，体积会小很多。路由懒加载因为项目中，体积占比最大的是Edit和Stat页面(编辑和统计页面)，所以考虑使用路由懒加载，拆分bundle，优化首页体积 router文件中，之前: import Edit from "../pages/question/Edit" ; import Stat from "../pages/question/Stat" ; 现在： const Edit = lazy (() => import ( "../pages/question/Edit" )); const Stat = lazy (() => import ( "../pages/question/Stat" )); 为了让生成的文件更加可读，可以改成下面这样: const Edit = lazy ( () => import ( /* webpackChunkName: "editPage" */ "../pages/question/Edit" ) ); const Stat ...

useMemo的使用场景

useMemo是用来缓存计算属性的。计算属性是函数的返回值，或者说那些以返回一个值为目标的函数。有些函数会需要我们手动去点击，有些函数是直接在渲染的时候就执行，在DOM区域被当作属性值一样去使用。后者被称为计算属性。 e.g. const Component = () => { const [ params1 , setParams1 ] = useState ( 0 ); const [ params2 , setParams2 ] = useState ( 0 ); //这种是需要我们手动去调用的函数 const handleFun1 = () => { console . log ( "我需要手动调用，你不点击我不执行" ); setParams1 (( val ) => val + 1 ); }; //这种被称为计算属性，不需要手动调用，在渲染阶段就会执行的。 const computedFun2 = () => { console . log ( "我又执行计算了" ); return params2 ; }; return ( < div onClick = { handleFun1 } > //每次重新渲染的时候我就会执行 computed: { computedFun2 () } </ div > ); }; 上面的代码中，在每次点击div的时候，因为setParams1的缘故，导致params1改变，整个组件都需要重新渲染，也导致comptedFunc2()也需要重新计算。如果computedFunc2的计算量很大，这时候重新计算会比较浪费。可以使用useMemo: const Com = () => { const [ params1 , setParams1 ] = useState ( 0 ); const [ params2 , setParams2 ] = useState ( 0 ); //这种是需要我们手动去调用的函数 const handleFun1 ...

王迎旭的博客

Search This Blog