如何在加载时滚动 React 页面？

Question

我想在 url (myapp.com#somevalue) 中传递一个值作为散列，并在页面加载时让页面滚动到该项目 - 正是使用散列的行为自互联网诞生以来的片段。我尝试使用 scrollIntoView 但在 iOS 上失败了。然后我只尝试 unsetting/setting window.location.hash 但似乎存在竞争条件。延迟大于600ms才有效

我想要一个更可靠的解决方案，不想引入不必要的延迟。当延迟太短时，它似乎滚动到所需的项目，但随后滚动到页面顶部。您不会看到此演示的效果，但它发生在我的实际应用程序 https://codesandbox.io/s/pjok544nrx 第 75 行

  componentDidMount() {
    let self = this;

    let updateSearchControl = hash => {
      let selectedOption = self.state.searchOptions.filter(
        option => option.value === hash
      )[0];
      if (selectedOption) {
        // this doesn't work with Safari on iOS
        // document.getElementById(hash).scrollIntoView(true);

        // this works if delay is 900 but not 500 ms
        setTimeout(() => {
          // unset and set the hash to trigger scrolling to target
          window.location.hash = null;
          window.location.hash = hash;
          // scroll back by the height of the Search box
          window.scrollBy(
            0,
            -document.getElementsByClassName("heading")[0].clientHeight
          );
        }, 900);
      } else if (hash) {
        this.searchRef.current.select.focus();
      }
    };

    // Get the hash
    // I want this to work as a Google Apps Script too which runs in
    // an iframe and has a special way to get the hash
    if (!!window["google"]) {
      let updateHash = location => {
        updateSearchControl(location.hash);
      };
      eval("google.script.url.getLocation(updateHash)");
    } else {
      let hash = window.location.hash.slice(1);
      updateSearchControl(hash);
    }
  }

编辑：我追踪到 re-renders 页面的 React 行，因此在它已经滚动到我告诉它进入 componentDidMount() 的位置后重置滚动位置。是 this one。 style[styleName] = styleValue; 在页面 re-rendered 时，它正在设置 react-select 框组件的输入框组件的宽度样式属性。执行此操作之前的堆栈跟踪看起来像

(anonymous) @   VM38319:1
setValueForStyles   @   react-dom.development.js:6426
updateDOMProperties @   react-dom.development.js:7587
updateProperties    @   react-dom.development.js:7953
commitUpdate    @   react-dom.development.js:8797
commitWork  @   react-dom.development.js:17915
commitAllHostEffects    @   react-dom.development.js:18634
callCallback    @   react-dom.development.js:149
invokeGuardedCallbackDev    @   react-dom.development.js:199
invokeGuardedCallback   @   react-dom.development.js:256
commitRoot  @   react-dom.development.js:18867
(anonymous) @   react-dom.development.js:20372
unstable_runWithPriority    @   scheduler.development.js:255
completeRoot    @   react-dom.development.js:20371
performWorkOnRoot   @   react-dom.development.js:20300
performWork @   react-dom.development.js:20208
performSyncWork @   react-dom.development.js:20182
requestWork @   react-dom.development.js:20051
scheduleWork    @   react-dom.development.js:19865
scheduleRootUpdate  @   react-dom.development.js:20526
updateContainerAtExpirationTime @   react-dom.development.js:20554
updateContainer @   react-dom.development.js:20611
ReactRoot.render    @   react-dom.development.js:20907
(anonymous) @   react-dom.development.js:21044
unbatchedUpdates    @   react-dom.development.js:20413
legacyRenderSubtreeIntoContainer    @   react-dom.development.js:21040
render  @   react-dom.development.js:21109
(anonymous) @   questionsPageIndex.jsx:10
./src/client/questionsPageIndex.jsx @   index.html:673
__webpack_require__ @   index.html:32
(anonymous) @   index.html:96
(anonymous) @   index.html:99

我不知道将滚动页面的指令移到哪里。它必须在设置这些样式之后发生，这发生在 componentDidMount() 之后。

编辑：我需要更好地明确我需要这样做的目的。抱歉之前没有这样做。

必备

这必须适用于所有常见的桌面和移动设备。

当页面加载时，可能会出现三种情况，具体取决于在 #:

之后 url 中提供的查询

1) 未提供任何查询 - 没有任何反应
2) 提供了有效的查询 - 页面立即滚动到所需的锚点并且页面的标题更改为选项的标签
3) 提供了无效的查询 - 将查询输入到搜索框中，搜索框被聚焦，菜单打开时选项受提供的查询限制，就好像它们是输入的一样。光标位于在查询末尾的搜索框中，以便用户可以修改查询。

有效的查询是指匹配其中一个选项的值的查询。无效查询是指不存在的查询。

浏览器的后退和前进按钮应相应地移动滚动位置。

只要从搜索框中选择一个选项，页面就会立即滚动到该锚点，查询应该清除并返回到占位符 "Search..."，url 应该更新，文档的标题应更改为选项的标签。

可选，但会很棒

选择后，菜单关闭，查询返回 "Search..."，

搜索框保留焦点，因此用户可以开始输入另一个查询。下次点击，菜单打开，选择前的Searchbox查询，恢复菜单的过滤器和菜单滚动位置（最优选），或者
搜索框失去焦点。下次focused，菜单打开，选择前的Search box query，恢复菜单的filter和menu scroll position（首选），或者
搜索框保留焦点，因此用户可以开始输入另一个查询。先前的查询和菜单滚动位置丢失。

Answer 1

您可以使用 https://www.npmjs.com/package/element.scrollintoviewifneeded-polyfill.

尽快在您的应用程序中导入库

import 'element.scrollintoviewifneeded-polyfill';

您可以在所有 dom 节点上使用方法 scrollIntoViewIfNeeded();。该库将填充该方法，以便您可以在所有浏览器上使用它。

我建议您将它与 react ref 一起使用，这样您就不必调用 getElementById 或其他文档方法来检索 dom 节点。

const ref = React.createRef();
<div id="somevalue" ref={ref} />

在您的 componentDidMount 中，您可以使用描述的相同方法来检索要滚动的 div 的 ID，获取关联的 ref 并调用

    ref.current.scrollIntoViewIfNeeded();

如果 ref 是正确的 div 引用，您显然可以将所有 ref 存储在一个映射中，而不是在您的组件方法中检索。

Answer 2

使用 react-scrollable-anchor 库可能更容易做到这一点：

import React from "react";
import ReactDOM from "react-dom";
import ScrollableAnchor from "react-scrollable-anchor";

class App extends React.Component {
  render() {
    return (
      <React.Fragment>
        <div style={{ marginBottom: 7000 }}>nothing to see here</div>
        <div style={{ marginBottom: 7000 }}>never mind me</div>
        <ScrollableAnchor id={"doge"}>
          <div>bork</div>
        </ScrollableAnchor>
      </React.Fragment>
    );
  }
}

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

你可以通过这里看到它的工作：https://zwoj0xw503.codesandbox.io/#doge

Answer 3

您可以通过使用 react-router-dom 的 HashRouter 和 React 的 ref.current.scrollIntoView() 或 window.scrollTo(ref.currrent.offsetTop) 来简化您的代码。

目前正在 Chrome (desktop/android)、Firefox（桌面）、Silk Browser（android）、Saumsung Internet（android）和 Safari 上进行测试和工作（iOS -- 需要注意的是它会立即跳转到所选内容）。虽然我能够测试并确认它在沙箱环境的 iframe 中工作，但您必须 adapt/test 它在独立的 iframe.

中

我还想指出您的方法非常 jQuery 并且您应该避免直接尝试利用或操纵 DOM and/or window.此外，您似乎在整个代码中使用了很多 let 变量，但它们保持不变。相反，它们应该是一个 const 变量，因为 React 每次重新渲染时都会评估变量，因此除非您计划在重新渲染过程中更改该变量，否则无需使用 let。

工作示例：https://v6y5211n4l.codesandbox.io

components/ScrollBar

import React, { Component } from "react";
import PropTypes from "prop-types";
import Helmet from "react-helmet";
import Select from "react-select";
import { withRouter } from "react-router-dom";
import "./styles.css";

const scrollOpts = {
  behavior: "smooth",
  block: "start"
};

class ScrollBar extends Component {
  constructor(props) {
    super(props);

    const titleRefs = props.searchOptions.map(
      ({ label }) => (this[label] = React.createRef())
    ); // map over options and use "label" as a ref name; ex: this.orange
    this.topWindow = React.createRef();
    this.searchRef = React.createRef();
    const pathname = props.history.location.pathname.replace(/\//g, ""); // set current pathname without the "/"

    this.state = {
      titleRefs,
      menuIsOpen: false,
      isValid: props.searchOptions.some(({ label }) => label === pathname), // check if the current pathname matches any of the labels
      pathname
    };
  }

  componentDidMount() {
    const { pathname, isValid } = this.state;
    if (isValid) this.scrollToElement(); // if theres a pathname and it matches a label, scroll to it
    if (!isValid && pathname) this.searchRef.current.select.focus(); // if there's a pathname but it's invalid, focus on the search bar
  }

  // allows us to update state based upon prop updates (in this case
  // we're looking for changes in the history.location.pathname)
  static getDerivedStateFromProps(props, state) {
    const nextPath = props.history.location.pathname.replace(/\//g, "");
    const isValid = props.searchOptions.some(({ label }) => label === nextPath);
    return state.pathname !== nextPath ? { pathname: nextPath, isValid } : null; // if the path has changed, update the pathname and whether or not it is valid
  }

  // allows us to compare new state to old state (in this case
  // we're looking for changes in the pathname)
  componentDidUpdate(prevProps, prevState) {
    if (this.state.pathname !== prevState.pathname) {
      this.scrollToElement();
    }
  }

  scrollToElement = () => {
    const { isValid, pathname } = this.state;
    const elem = isValid ? pathname : "topWindow";
    setTimeout(() => {
     window.scrollTo({
        behavior: "smooth",
        top: this[elem].current.offsetTop - 45
      });
    }, 100);
  };

  onInputChange = (options, { action }) => {
    if (action === "menu-close") {
      this.setState({ menuIsOpen: false }, () =>
        this.searchRef.current.select.blur()
      );
    } else {
      this.setState({ menuIsOpen: true });
    }
  };

  onChange = ({ value }) => {
    const { history } = this.props;
    if (history.location.pathname.replace(/\//g, "") !== value) { // if the select value is different than the previous selected value, update the url -- required, otherwise, react-router will complain about pushing the same pathname/value that is current in the url
      history.push(value);
    }
    this.searchRef.current.select.blur();
  };

  onFocus = () => this.setState({ menuIsOpen: true });

  render() {
    const { pathname, menuIsOpen, titleRefs } = this.state;
    const { searchOptions, styles } = this.props;

    return (
      <div className="container">
        <Helmet title={this.state.pathname || "Select an option"} />
        <div className="heading">
          <Select
            placeholder="Search..."
            isClearable={true}
            isSearchable={true}
            options={searchOptions}
            defaultInputValue={pathname}
            onFocus={this.onFocus}
            onInputChange={this.onInputChange}
            onChange={this.onChange}
            menuIsOpen={menuIsOpen}
            ref={this.searchRef}
            value={null}
            styles={styles || {}}
          />
        </div>
        <div className="fruits-list">
          <div ref={this.topWindow} />
          {searchOptions.map(({ label, value }, key) => (
            <div key={value} id={value}>
              <p ref={titleRefs[key]}>{label}</p>
              {[1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14].map(num => (
                <p key={num}>{num}</p>
              ))}
            </div>
          ))}
        </div>
      </div>
    );
  }
}

ScrollBar.propTypes = {
  searchOptions: PropTypes.arrayOf(
    PropTypes.shape({
      label: PropTypes.string.isRequired,
      value: PropTypes.string.isRequired
    }).isRequired
  ).isRequired,
  styles: PropTypes.objectOf(PropTypes.func)
};

export default withRouter(ScrollBar);

index.js

import React from "react";
import { render } from "react-dom";
import { HashRouter } from "react-router-dom";
import Helmet from "react-helmet";
import ScrollBar from "../src/components/ScrollBar";

const config = {
  htmlAttributes: { lang: "en" },
  title: "My App",
  titleTemplate: "Scroll Search - %s",
  meta: [
    {
      name: "description",
      content: "The best app in the world."
    }
  ]
};

const searchOptions = [
  {
    label: "apple",
    value: "apple"
  },
  {
    label: "orange",
    value: "orange"
  },
  {
    label: "banana",
    value: "banana"
  },
  {
    label: "strawberry",
    value: "strawberry"
  }
];

const styles = {
  menu: base => ({ ...base, width: "100%", height: "75vh" }),
  menuList: base => ({ ...base, minHeight: "75vh" }),
  option: base => ({ ...base, color: "blue" })
};

const App = () => (
  <HashRouter>
    <Helmet {...config} />
    <ScrollBar searchOptions={searchOptions} styles={styles} />
  </HashRouter>
);

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

Answer 4

我把它放在组件文件中导入之后：

let initialValidSlug = '';

window.addEventListener('load', () => {
  window.location.hash = '';
  window.location.hash = (initialValidSlug ? initialValidSlug : '');
  window.scrollBy(0, -document.getElementsByClassName("heading")[0].clientHeight);
  console.log('window.addEventListener')
});

给我的 componentDidMount():

  componentDidMount() {
    const { pathname, isValid } = this.state;
    if(!isValid && pathname) {               // if there's a pathname but it's invalid,
      this.searchRef.current.select.focus(); // focus on the search bar
    }
    initialValidSlug = pathname;  // sets the value to be used in the $.ready() above
  }

如何在加载时滚动 React 页面？

How to scroll a React page when it loads?

reactjs

react-select

必备

可选，但会很棒