如何获得全高？答案

【问题标题】：How to get the full height?如何获得全高？
【发布时间】：2020-08-09 00:32:26
【问题描述】：

我正在尝试获取页面的完整高度以将其应用于样式，特别是darkMask 类。

我需要高度，因为当我在页眉内执行操作时，整个页面都会应用一个深色层，但调用该操作后出现的元素除外。

现在，由于 useRef 钩子，我得到了高度，然后我把它放到了容器中，但这并没有给我完整的高度

import { useContext, useState, useRef, useEffect } from 'react';
import { useRouter } from 'next/router';
import { Header } from '../Header';
import { SearchToggleContext } from '../../contexts/SearchToggleContext';
import styles, { globalStyles } from './styles';

export const Layout = ({ children }) => {
  const [height, setHeight] = useState();
  const mainContainer = useRef(null);
  const { isOpenSearch } = useContext(SearchToggleContext);
  const router = useRouter();

  useEffect(() => {
    if (mainContainer.current) {
      setHeight(mainContainer.current.offsetHeight);
    }
  }, [router]);

  return (
    <>
      <div className='darkMask' />
      <Header />
      <main ref={mainContainer}>{children}</main>

      <style jsx global>
        {globalStyles}
      </style>
      <style jsx>{styles}</style>
      <style jsx>{`
        .darkMask {
          display: ${isOpenSearch ? 'block' : 'none'};
          height: ${height}px;
        }
      `}</style>
    </>
  );
};

/* Styles of layout */
import css from 'styled-jsx/css';

export const globalStyles = css.global`
  html,
  body {
    height: 100%;
    width: 100%;
    font-family: -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Oxygen,
      Ubuntu, Cantarell, Fira Sans, Droid Sans, Helvetica Neue, sans-serif;
  }

  a {
    color: inherit;
    text-decoration: none;
  }

  * {
    box-sizing: border-box;
    padding: 0;
    margin: 0;
  }

  .navbarItem {
    margin-right: 2em;
  }
`;

export default css`
  main {
    height: calc(100vh - 80px);
    width: 100%;
    top: 80px;
    position: absolute;
  }

  .darkMask {
    position: relative;
    z-index: 4;
    width: 100%;
    top: 80px;
    position: absolute;
    background-color: rgba(45, 45, 45, 0.9);
  }
`;

/* _app.js file */
import { Layout } from '../components/Layout';
import { SearchToggleContextProvider } from '../contexts/SearchToggleContext';

function MyApp({ Component, pageProps }) {
  return (
    <>
      <SearchToggleContextProvider>
        <Layout>
          <Component {...pageProps} />
        </Layout>
      </SearchToggleContextProvider>
    </>
  );
}

export default MyApp;

【问题讨论】：

标签： javascript reactjs next.js server-side-rendering

【解决方案1】：

您可以使用document.body.offsetHeight 获取整个<body> 元素的高度。

const { useState, useEffect } = React;

function App() {
  const [height, setHeight] = useState(null);
  const [count, setCount] = useState(0);

  useEffect(() => {
    setHeight(document.body.offsetHeight);
  }, [count]);

  const elements = [];

  for (let i = 0; i < count; i++) {
    elements.push(<p key={i}>{`Element ${i}`}</p>);
  }

  return (
    <div className="App">
      <span>{`Document height: ${height} px`}</span>

      <div>
        <button onClick={() => setCount(count + 1)}>Add element</button>
        {elements}
      </div>
    </div>
  );
}

ReactDOM.render(<App />, document.getElementById("root"));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>

【讨论】：