真是个好问题！我真的很喜欢为此提出解决方案。
由于您想为菜单状态和复选框状态提供初始状态，我认为在<Menu> 级别（甚至更高！）上控制两者的状态是个好主意。这不仅使从父级定义初始状态变得容易，而且如果您将来需要一些更复杂的菜单或复选框行为，它还可以为您提供更大的灵活性。
由于菜单的结构是递归的，我认为菜单状态的递归结构效果很好。在我进入代码之前，这里有一个简短的 GIF，我希望它有助于解释状态的样子：
演示
这里是游乐场 sn-p：
const loadMenu = () =>
Promise.resolve([
{
id: "1",
name: "One",
children: [
{
id: "1.1",
name: "One - one",
children: [
{ id: "1.1.1", name: "One - one - one" },
{ id: "1.1.2", name: "One - one - two" },
{ id: "1.1.3", name: "One - one - three" }
]
}
]
},
{ id: "2", name: "Two", children: [{ id: "2.1", name: "Two - one" }] },
{
id: "3",
name: "Three",
children: [
{
id: "3.1",
name: "Three - one",
children: [
{
id: "3.1.1",
name: "Three - one - one",
children: [
{
id: "3.1.1.1",
name: "Three - one - one - one",
children: [
{ id: "3.1.1.1.1", name: "Three - one - one - one - one" }
]
}
]
}
]
}
]
},
{ id: "4", name: "Four" },
{
id: "5",
name: "Five",
children: [
{ id: "5.1", name: "Five - one" },
{ id: "5.2", name: "Five - two" },
{ id: "5.3", name: "Five - three" },
{ id: "5.4", name: "Five - four" }
]
},
{ id: "6", name: "Six" }
]);
const { Component, Fragment } = React;
const { Button, Collapse, Input } = Reactstrap;
const replaceNode = (replacer, node, idPath, i) => {
if (i <= idPath.length && !node) {
// Not at target node yet, create nodes in between
node = {};
}
if (i > idPath.length) {
// Reached target node
return replacer(node);
}
// Construct ID that matches this depth - depth meaning
// the amount of dots in between the ID
const id = idPath.slice(0, i).join(".");
return {
...node,
// Recurse
[id]: replaceNode(replacer, node[id], idPath, i + 1)
};
};
const replaceNodeById = (node, id, visitor) => {
// Pass array of the id's parts instead of working on the string
// directly - easy way to handle multi-number ID parts e.g. 3.1.15.32
return replaceNode(visitor, node, id.split("."), 1);
};
const expandedNode = () => ({});
const unexpandedNode = () => undefined;
const toggleNodeById = (node, id) =>
replaceNodeById(node, id, oldNode =>
oldNode ? unexpandedNode() : expandedNode()
);
const expandNodeById = (node, id) =>
replaceNodeById(node, id, oldNode => expandedNode());
class Menu extends Component {
constructor(props) {
super(props);
this.state = {
menuItems: [],
openMenus: {},
checkedMenus: {}
};
this.handleMenuToggle = this.handleMenuToggle.bind(this);
this.handleChecked = this.handleChecked.bind(this);
}
render() {
const { menuItems, openMenus, checkedMenus } = this.state;
return (
<div
style={{
display: "flex",
flexDirection: "row",
columnCount: 3,
justifyContent: "space-between"
}}
>
<div style={{ paddingTop: "10px" }}>
<MenuItemContainer
openMenus={openMenus}
menuItems={menuItems}
onMenuToggle={this.handleMenuToggle}
checkedMenus={checkedMenus}
onChecked={this.handleChecked}
/>
</div>
<div style={{ padding: "10px", marginLeft: "auto" }}>
<p>Menu state</p>
<pre>{JSON.stringify(openMenus, null, 2)}</pre>
</div>
<div style={{ padding: "10px", width: "177px" }}>
<p>Checkbox state</p>
<pre>{JSON.stringify(checkedMenus, null, 2)}</pre>
</div>
</div>
);
}
componentDidMount() {
const { initialOpenMenuId, initialCheckedMenuIds } = this.props;
loadMenu().then(menuItems => {
const initialMenuState = {};
this.setState({
menuItems,
openMenus: expandNodeById(initialMenuState, initialOpenMenuId),
checkedMenus: initialCheckedMenuIds.reduce(
(acc, val) => ({ ...acc, [val]: true }),
{}
)
});
});
}
handleMenuToggle(toggledId) {
this.setState(({ openMenus }) => ({
openMenus: toggleNodeById(openMenus, toggledId)
}));
}
handleChecked(toggledId) {
this.setState(({ checkedMenus }) => ({
checkedMenus: {
...checkedMenus,
[toggledId]: checkedMenus[toggledId] ? unexpandedNode() : expandedNode()
}
}));
}
}
function MenuItemContainer({
openMenus,
onMenuToggle,
checkedMenus,
onChecked,
menuItems = []
}) {
if (!menuItems.length) return null;
const renderMenuItem = menuItem => (
<li key={menuItem.id}>
<MenuItem
openMenus={openMenus}
onMenuToggle={onMenuToggle}
checkedMenus={checkedMenus}
onChecked={onChecked}
{...menuItem}
/>
</li>
);
return <ul>{menuItems.map(renderMenuItem)}</ul>;
}
class MenuItem extends Component {
constructor(props) {
super(props);
this.handleToggle = this.handleToggle.bind(this);
this.handleChecked = this.handleChecked.bind(this);
}
render() {
const {
children,
name,
id,
openMenus,
onMenuToggle,
checkedMenus,
onChecked
} = this.props;
const isLastChild = !children;
return (
<Fragment>
<Button onClick={isLastChild ? this.handleChecked : this.handleToggle}>
{name}
</Button>
{isLastChild && (
<Input
addon
type="checkbox"
onChange={this.handleChecked}
checked={!!checkedMenus[id]}
value={id}
/>
)}
<Collapse isOpen={openMenus ? !!openMenus[id] : false}>
<MenuItemContainer
menuItems={children}
// Pass down child menus' state
openMenus={openMenus && openMenus[id]}
onMenuToggle={onMenuToggle}
checkedMenus={checkedMenus}
onChecked={onChecked}
/>
</Collapse>
</Fragment>
);
}
handleToggle() {
this.props.onMenuToggle(this.props.id);
}
handleChecked() {
this.props.onChecked(this.props.id);
}
}
ReactDOM.render(
<Menu initialOpenMenuId="3.1.1.1" initialCheckedMenuIds={["3.1.1.1.1"]} />,
document.getElementById("root")
);
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.4.1/css/bootstrap.min.css" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/reactstrap/8.4.1/reactstrap.min.js"></script>
<div id="root"></div>
回答
下面的代码演练。
const loadMenu = () =>
Promise.resolve([
{
id: "1",
name: "One",
children: [
{
id: "1.1",
name: "One - one",
children: [
{ id: "1.1.1", name: "One - one - one" },
{ id: "1.1.2", name: "One - one - two" },
{ id: "1.1.3", name: "One - one - three" }
]
}
]
},
{ id: "2", name: "Two", children: [{ id: "2.1", name: "Two - one" }] },
{
id: "3",
name: "Three",
children: [
{
id: "3.1",
name: "Three - one",
children: [
{
id: "3.1.1",
name: "Three - one - one",
children: [
{
id: "3.1.1.1",
name: "Three - one - one - one",
children: [
{ id: "3.1.1.1.1", name: "Three - one - one - one - one" }
]
}
]
}
]
}
]
},
{ id: "4", name: "Four" },
{
id: "5",
name: "Five",
children: [
{ id: "5.1", name: "Five - one" },
{ id: "5.2", name: "Five - two" },
{ id: "5.3", name: "Five - three" },
{ id: "5.4", name: "Five - four" }
]
},
{ id: "6", name: "Six" }
]);
const { Component, Fragment } = React;
const { Button, Collapse, Input } = Reactstrap;
const replaceNode = (replacer, node, idPath, i) => {
if (i <= idPath.length && !node) {
// Not at target node yet, create nodes in between
node = {};
}
if (i > idPath.length) {
// Reached target node
return replacer(node);
}
// Construct ID that matches this depth - depth meaning
// the amount of dots in between the ID
const id = idPath.slice(0, i).join(".");
return {
...node,
// Recurse
[id]: replaceNode(replacer, node[id], idPath, i + 1)
};
};
const replaceNodeById = (node, id, visitor) => {
// Pass array of the id's parts instead of working on the string
// directly - easy way to handle multi-number ID parts e.g. 3.1.15.32
return replaceNode(visitor, node, id.split("."), 1);
};
const expandedNode = () => ({});
const unexpandedNode = () => undefined;
const toggleNodeById = (node, id) =>
replaceNodeById(node, id, oldNode =>
oldNode ? unexpandedNode() : expandedNode()
);
const expandNodeById = (node, id) =>
replaceNodeById(node, id, oldNode => expandedNode());
class Menu extends Component {
constructor(props) {
super(props);
this.state = {
menuItems: [],
openMenus: {},
checkedMenus: {}
};
this.handleMenuToggle = this.handleMenuToggle.bind(this);
this.handleChecked = this.handleChecked.bind(this);
}
render() {
const { menuItems, openMenus, checkedMenus } = this.state;
return (
<MenuItemContainer
openMenus={openMenus}
menuItems={menuItems}
onMenuToggle={this.handleMenuToggle}
checkedMenus={checkedMenus}
onChecked={this.handleChecked}
/>
);
}
componentDidMount() {
const { initialOpenMenuId, initialCheckedMenuIds } = this.props;
loadMenu().then(menuItems => {
const initialMenuState = {};
this.setState({
menuItems,
openMenus: expandNodeById(initialMenuState, initialOpenMenuId),
checkedMenus: initialCheckedMenuIds.reduce(
(acc, val) => ({ ...acc, [val]: true }),
{}
)
});
});
}
handleMenuToggle(toggledId) {
this.setState(({ openMenus }) => ({
openMenus: toggleNodeById(openMenus, toggledId)
}));
}
handleChecked(toggledId) {
this.setState(({ checkedMenus }) => ({
checkedMenus: {
...checkedMenus,
[toggledId]: checkedMenus[toggledId] ? unexpandedNode() : expandedNode()
}
}));
}
}
function MenuItemContainer({
openMenus,
onMenuToggle,
checkedMenus,
onChecked,
menuItems = []
}) {
if (!menuItems.length) return null;
const renderMenuItem = menuItem => (
<li key={menuItem.id}>
<MenuItem
openMenus={openMenus}
onMenuToggle={onMenuToggle}
checkedMenus={checkedMenus}
onChecked={onChecked}
{...menuItem}
/>
</li>
);
return <ul>{menuItems.map(renderMenuItem)}</ul>;
}
class MenuItem extends Component {
constructor(props) {
super(props);
this.handleToggle = this.handleToggle.bind(this);
this.handleChecked = this.handleChecked.bind(this);
}
render() {
const {
children,
name,
id,
openMenus,
onMenuToggle,
checkedMenus,
onChecked
} = this.props;
const isLastChild = !children;
return (
<Fragment>
<Button onClick={isLastChild ? this.handleChecked : this.handleToggle}>
{name}
</Button>
{isLastChild && (
<Input
addon
type="checkbox"
onChange={this.handleChecked}
checked={!!checkedMenus[id]}
value={id}
/>
)}
<Collapse isOpen={openMenus ? !!openMenus[id] : false}>
<MenuItemContainer
menuItems={children}
// Pass down child menus' state
openMenus={openMenus && openMenus[id]}
onMenuToggle={onMenuToggle}
checkedMenus={checkedMenus}
onChecked={onChecked}
/>
</Collapse>
</Fragment>
);
}
handleToggle() {
this.props.onMenuToggle(this.props.id);
}
handleChecked() {
this.props.onChecked(this.props.id);
}
}
ReactDOM.render(
<Menu initialOpenMenuId="3.1.1.1" initialCheckedMenuIds={["3.1.1.1.1"]} />,
document.getElementById("root")
);
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.4.1/css/bootstrap.min.css" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/reactstrap/8.4.1/reactstrap.min.js"></script>
<div id="root"></div>
演练
在开始之前，我必须说我冒昧地更改了一些代码以使用现代 JavaScript 功能，例如 object destructuring，
array destructuring、rest 和 default values。
创建状态
所以。由于菜单项的 ID 是由点分隔的数字，因此我们可以在构造状态时利用这一点。状态本质上是一个树状结构，每个子菜单都是其父级的子菜单，叶节点（“最后一个菜单”或“最深的菜单”）如果展开，则具有 {} 的值，或者undefined 如果没有。以下是菜单初始状态的构造方式：
<Menu initialOpenMenuId="3.1.1.1" initialCheckedMenuIds={["3.1.1.1.1"]} />
// ...
loadMenu().then(menuItems => {
const initialMenuState = {};
this.setState({
menuItems,
openMenus: expandNodeById(initialMenuState, initialOpenMenuId),
checkedMenus: initialCheckedMenuIds.reduce(
(acc, val) => ({ ...acc, [val]: true }),
{}
)
});
});
// ...
const expandedNode = () => ({});
const unexpandedNode = () => undefined;
const toggleNodeById = (node, id) =>
replaceNodeById(node, id, oldNode =>
oldNode ? unexpandedNode() : expandedNode()
);
const expandNodeById = (node, id) =>
replaceNodeById(node, id, oldNode => expandedNode());
const replaceNodeById = (node, id, visitor) => {
// Pass array of the id's parts instead of working on the string
// directly - easy way to handle multi-number ID parts e.g. 3.1.15.32
return replaceNode(visitor, node, id.split("."), 1);
};
const replaceNode = (replacer, node, idPath, i) => {
if (i <= idPath.length && !node) {
// Not at target node yet, create nodes in between
node = {};
}
if (i > idPath.length) {
// Reached target node
return replacer(node);
}
// Construct ID that matches this depth - depth meaning
// the amount of dots in between the ID
const id = idPath.slice(0, i).join(".");
return {
...node,
// Recurse
[id]: replaceNode(replacer, node[id], idPath, i + 1)
};
};
让我们一点一点地分解。
const expandedNode = () => ({});
const unexpandedNode = () => undefined;
这些只是我们定义的便利函数，因此我们可以轻松更改用于表示展开和未展开节点的值。与仅在代码中使用文字 {} 或 undefined 相比，它还使代码更具可读性。展开和未展开的值也可以是true 和false，重要的是展开的节点是truthy，而未展开的节点是假的。稍后再详细介绍。
const toggleNodeById = (node, id) =>
replaceNodeById(node, id, oldNode =>
oldNode ? unexpandedNode() : expandedNode()
);
const expandNodeById = (node, id) =>
replaceNodeById(node, id, oldNode => expandedNode());
这些功能让我们可以在菜单状态下切换或展开特定菜单。第一个参数是菜单状态本身，第二个是菜单的字符串 ID（例如"3.1.1.1.1"），第三个是执行替换的函数。把它想象成你传递给.map() 的函数。替换器功能与实际的递归树迭代分离，以便您以后可以轻松实现更多功能 - 例如，如果您希望某些特定菜单不展开，您只需传入一个返回 unexpandedNode() 的函数。
const replaceNodeById = (node, id, visitor) => {
// Pass array of the id's parts instead of working on the string
// directly - easy way to handle multi-number ID parts e.g. 3.1.15.32
return replaceNode(visitor, node, id.split("."), 1);
};
这个函数被前两个函数用来提供一个更干净的界面。 ID 在此处由点 (.) 分割，这为我们提供了 ID 部分的数组。下一个函数直接操作这个数组而不是 ID 字符串，因为这样我们就不需要做.indexOf('.') shenanigans。
const replaceNode = (replacer, node, idPath, i) => {
if (i <= idPath.length && !node) {
// Not at target node yet, create nodes in between
node = {};
}
if (i > idPath.length) {
// Reached target node
return replacer(node);
}
// Construct ID that matches this depth - depth meaning
// the amount of dots in between the ID
const id = idPath.slice(0, i).join(".");
return {
...node,
// Recurse
[id]: replaceNode(replacer, node[id], idPath, i + 1)
};
};
replaceNode 函数是问题的核心。它是一个递归函数，从旧菜单树生成新树，用提供的替换函数替换旧目标节点。如果树缺少介于两者之间的部分，例如当树是{} 但我们想要替换节点3.1.1.1 时，它会在它们之间创建父节点。有点像mkdir -p，如果你熟悉这个命令的话。
这就是菜单状态。复选框状态 (checkedMenus) 基本上只是一个索引，如果选中了一个项目，则键是 ID，值是 true。这种状态不是递归的，因为它们不需要被取消检查或递归检查。如果您决定要显示该菜单项下的某些内容已被选中的指示符，一个简单的解决方案是将复选框状态更改为像菜单状态一样递归。
渲染树
<Menu> 组件将状态向下传递给<MenuItemContainer>，它会呈现<MenuItem>s。
function MenuItemContainer({
openMenus,
onMenuToggle,
checkedMenus,
onChecked,
menuItems = []
}) {
if (!menuItems.length) return null;
const renderMenuItem = menuItem => (
<li key={menuItem.id}>
<MenuItem
openMenus={openMenus}
onMenuToggle={onMenuToggle}
checkedMenus={checkedMenus}
onChecked={onChecked}
{...menuItem}
/>
</li>
);
return <ul>{menuItems.map(renderMenuItem)}</ul>;
}
<MenuItemContainer> 组件与原始组件没有太大区别。不过，<MenuItem> 组件看起来确实有点不同。
class MenuItem extends Component {
constructor(props) {
super(props);
this.handleToggle = this.handleToggle.bind(this);
this.handleChecked = this.handleChecked.bind(this);
}
render() {
const {
children,
name,
id,
openMenus,
onMenuToggle,
checkedMenus,
onChecked
} = this.props;
const isLastChild = !children;
return (
<Fragment>
<Button onClick={isLastChild ? this.handleChecked : this.handleToggle}>
{name}
</Button>
{isLastChild && (
<Input
addon
type="checkbox"
onChange={this.handleChecked}
checked={!!checkedMenus[id]}
value={id}
/>
)}
<Collapse isOpen={openMenus ? !!openMenus[id] : false}>
<MenuItemContainer
menuItems={children}
// Pass down child menus' state
openMenus={openMenus && openMenus[id]}
onMenuToggle={onMenuToggle}
checkedMenus={checkedMenus}
onChecked={onChecked}
/>
</Collapse>
</Fragment>
);
}
handleToggle() {
this.props.onMenuToggle(this.props.id);
}
handleChecked() {
this.props.onChecked(this.props.id);
}
}
这里的关键部分是：openMenus={openMenus && openMenus[id]}。我们只传递包含当前项的子项的状态树，而不是传递整个菜单状态。这允许组件非常容易地检查它是否应该打开或折叠 - 只需检查是否从对象中找到了它自己的 ID (openMenus ? !!openMenus[id] : false)！
如果它是菜单中最深的项目，我还更改了切换按钮以切换复选框而不是菜单状态 - 如果这不是您要查找的内容，则可以很快改回来。
我还在这里使用!! 将{} 和undefined 从菜单状态强制转换为true 或false。这就是为什么我说只有它们是真的还是假的才重要。 reactstrap 组件似乎需要明确的 true 或 false 而不是真/假，这就是它存在的原因。
最后：
ReactDOM.render(
<Menu initialOpenMenuId="3.1.1.1" initialCheckedMenuIds={["3.1.1.1.1"]} />,
document.getElementById("root")
);
这里我们将初始状态传递给<Menu>。 initialOpenMenuId 也可以是一个数组（或 initialCheckedMenuIds 可以是单个字符串），但这符合问题的规范。
改进空间
目前的解决方案一直向下传递大量状态，例如onMenuToggle 和onChecked 回调，以及非递归的checkedMenus 状态。这些可以利用 React 的 Context。