Js recursion cannot return data

        const tree = {
            id:"root",
            children:[
                {id:1,children:["id1"]},
                {id:2,children:["id2"]},
                {id:3,children:["id3"]},
                {id:4,children:[
                    {id:5,children:["id4id5"]}
                ]},
                {id:6,children:[
                    {id:7,children:[
                        {id:8,children:["id4id5"]}
                    ]}
                ]}
            ]
        }



        function search(id,arr){
            let asd = {};
            arr.forEach((val,ind,arr)=>{
                if(!val.id) {asd = "meiyou";return}    
                if(val.id == id){
                    asd["id"] = val.id;
                    asd["children"] = val.children;
                    console.log(asd); // 
                    return;
                }else{
                    search(id,val.children);
                }
            });
            return asd;
        }

        var result = search(5,tree.children);
        console.log(result); // {}
The first layer of the

array can return normally, and if it is deeper, it will return {} and ask for the correct answer

.
Javascript
Apr.08,2022

there are still a lot of problems. Do not return in the callback function of forEach , because that is meaningless. It is a callback function and does not prevent forEach from continuing execution.
if id is not repeated, you don't need to traverse all the nodes, because that doesn't make sense. 

        function search(id, node) {
            if (node.children) {
                for (let nc of node.children) {
                    if (nc.id === id) {
                        return nc;
                    } else {
                        let same = search(id, nc);
                        if (same) return same;
                    }
                }
            }
            return null;
        }


        var result = search(5, tree);
        console.log('result', result); // {}

the variable asd cannot be defined in the function search . In this way, each recursion will reassign the asd to {} , and the search function is also problematic. Please refer to the following code 

    const tree = {
        id:"root",
        children:[
            {id:1,children:['id1']},
            {id:2,children:['id2']},
            {id:3,children:['id3']},
            {id:4,children:[
                {id:5,children:['id4id5']}
            ]},
            {id:6,children:[
                {id:7,children:[
                    {id:8,children:['id4id5']}
                ]}
            ]}
        ]
    }


    // 
    let asd = {}
    
    function search(id,arr){
        arr.forEach((val,ind,arr)=>{
            if(val.id && val.id == id){
                asd['id'] = val.id;
                asd['children'] = val.children;
                console.log(asd); // 
            }else{
                if(val.children){
                    search(id,val.children);
                }
            }
        });
        return asd;
    }

    var result = search(5,tree.children);
    console.log(result); // {id: 5, children: Array(1)}

because the asd after your second layer is the local variable of the inner layer, when you return, the outer layer does not get this value.

you can put asd outside the search function as a global variable;
, of course, it's better to return

with a value in the search.

Previous: A problem of layout

Next: Double for Loop in vue, dynamic data

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
© 2021 CodesHelper
Advertising Contact us About us
Menu