反应递归的多级下拉列表

Question

I am building a multilevel menu and want to use recursion to display the menu. Something like the multi-level dropdown from here .

In my code my menu looks like this.

const menu = [
  {
    name: 'Man Utd',
    menu: [
       {
          name: 'Stadium'
       },
       {
          name: 'About'
       }
    ]
  },
  {
    name: 'Liverpool',
    menu: [
       {
           name: 'Contact'
       }
    ]
  }
];

which I then pass this into my react component.

const Dropdown = ({ menu }) => {
    const renderMenu = (items) => {
        return items.map((item: any, index: any) => {
            return (
                <div>
                    {item.menu ? renderMenu() : item.name}
                </div>
            )
        })
    }

    return (renderMenu(menu));
}

the issue here is that it is causing an infinite loop.

Can anyone advise me as to how I can improve this?

Answer 1

You need to pass item.menu as argument to renderMenu when you recursively render the menu.

Example

 const menu = [ { name: "Man Utd", menu: [ { name: "Stadium" }, { name: "About" } ] }, { name: "Liverpool", menu: [ { name: "Contact" } ] } ]; const Dropdown = ({ menu }) => { const renderMenu = items => { return items.map((item: any, index: any) => { return ( <div style={{ marginLeft: 10 }}> {item.name} {item.menu ? renderMenu(item.menu) : null} </div> ); }); }; return <div>{renderMenu(menu)}</div>; }; ReactDOM.render(<Dropdown menu={menu} />, document.getElementById("root")); 

 <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> <div id="root"></div> 

Answer 2

Your not passing down anything to renderMenu. You should call renderMenu(item.menu)