Recursive Function Returns Undefined

Recursive function returns undefined

In this arm of your function:

if (taxWage > minWage) {
    // calculates tax recursively calling two other functions difference() and taxStep() 
    tax = tax + difference(taxWage) * taxStep(taxWage);
    var newSalary = taxWage - difference(taxWage);
    taxes(tax, newSalary); 
}

you are not returning a value from the function or setting returnTax. When you don't return anything, the return value is undefined.

Perhaps, you want this:

if (taxWage > minWage) {
    // calculates tax recursively calling two other functions difference() and taxStep() 
    tax = tax + difference(taxWage) * taxStep(taxWage);
    var newSalary = taxWage - difference(taxWage);
    return taxes(tax, newSalary); 
}

Javascript recursive function returns undefined

areas.forEach(a => { return fron the lambda function. it is not returning from parent function. Use basic for loop to break loop.

For more info, you can read my blog: how-to-break-the-loop-in-javascript

class AreaManager {

  constructor() {

    this.areas = [];

    this.areas.push(new Area("Area1", this));

    this.areas[0].areas.push(new Area("AreaABC", this.areas[0]));

    this.areas[0].areas[0].areas.push(

      new Area("AreaABC123", this.areas[0].areas[0])

    );

    this.areas[0].areas.push(new Area("AreaDEF", this.areas[0]));

  }

  findAreaById(id, areas = this.areas) {

    let merged = [];

    for (let i = 0; i < areas.length; i++) {

      if (areas[i].id == id) return areas[i];

      merged = merged.concat(areas[i].areas);

    }

    return this.findAreaById(id, merged);

  }

}

class Area {

  constructor(id, parent) {

    this.id = id;

    this.areas = [];

  }

}

var _Manager;

function InitManager() {

  _Manager = new AreaManager();

}

function GetSomeArea() {

  var searchID = "AreaDEF";

  var areaObject = _Manager.findAreaById(searchID);

  console.log(areaObject); //this is always undefined

}

InitManager();

GetSomeArea();

Recursive function on sorted array returns undefined

You're not calling the recursive function from outside of the function.

const sortArray = (mainArr) => {
    let acc = [];
    console.log(acc, "acc");
    const recursive = (arr) => {

        if (arr.length > 1) {
            console.log("inside func2 ", acc);
            let likeArr = singArr(arr, arr[0]);
            console.log(likeArr, "like");
            arr = deleteVal(arr, arr[0]);
            acc.push(likeArr);
            return recursive(mainArr);
        }
        else {
            return acc;
        }
    }
    
    return recursive(mainArr)
};

Also, I believe the code posted doesn't return the desired output. You can probably do the following:

const array1 = [1,2,4,591,392,391,2,5,10,2,1,1,1,20,20];
array1.sort((a,b) => a-b);

const map = new Map();

array1.forEach((item) => { 
    if(map.has(item)) {
        const storedItem = map.get(item);
        map.set(item, Array.isArray(storedItem) ? [...storedItem, item] : [storedItem, item])
    } else {
        map.set(item, item);
    }
});

console.log(Array.from(map.values()))

JavaScript + recursive function returning undefined

You are simply the call to return on the recursive call. Also, you should test whether its result is defined. If yes, you can return it, or continue looping if not.

var h = hasId(container, 'head');
var l = hasId(container, 'left');
var r = hasId(container, 'right');

console.log(h + " : " + r + " : " + l);
//[object HTMLDivElement] : undefined : undefined

function hasId(ele, id) {
    for (var i = 0; i < ele.childNodes.length; i++) {
        var child = ele.childNodes[i];
        if(child.id == id) return child;
        else {
          var next = hasId(child, id);
          if(next) return next;
        };
    }
}​

Javascript recursion function returning undefined

Your recursive call have to return the value to the caller

function searchLeft(node, path) {
    if (typeof node.left == 'undefined') {
        console.log(path);
        return path;
    }
    node = JSON.parse(JSON.stringify(node.left));
    path.push(node.data);
    return searchLeft(node, path); //here return
}

Why is my recursive function returning undefined?

forEach does not return a value. If you want to sum all the results, you can use Array#reduce. In addition, you can set the accumulator's initial value to 0 by passing in a second argument, so you can remove the check for the array's length being 0.

function findNestedBags(key, color, data) {
    if (data[key].includes(color)) {
        return 1
    } else {
        return data[key].reduce((acc,item) => {
            return acc + findNestedBags(item, color, data)
        }, 0)
    }
}

Recursive function returns undefined regardless of enough return statements

forEach returns undefined, so

return node.forEach(el => {
  return recurseFind(el, id);
});

will always return undefined, no matter what the recursive calls find.

I'd use a for loop instead, and if a match is found, return it:

let animals = [

  {

    name: "dogs",

    id: 1,

    children: [

      {

        name: "lessie",

        id: 2

      },

      {

        name: "bark-a-lot",

        id: 3

      }

    ]

  },

  {

    name: "cats",

    id: 4,

    children: [

      {

        name: "meows-a-lot",

        id: 5,

        children: [

          {

            name: "meows-a-lot-in-the-morning",

            id: 6

          }

        ]

      },

      {

        name: "whisk-ass",

        id: 7

      }

    ]

  }

];

function recurseFind(node, id) {

  if (Array.isArray(node)) {

    for (const el of node) {

      const result = recurseFind(el, id);

      if (result) return result;

    }

  } else {

    if (node.id === id) {

      return node;

    } else if (node.children) {

      for (const child of node.children) {

        const result = recurseFind(child, id);

        if (result) return result;

      }

    }

  }

}

const found = recurseFind(animals, 6) || 'not found';

console.log("found", found);

Recursive async function returning undefined

Essentially the only problem with your code is that you don't await the results from you async function comp(). map() will return an array of Promises and you will need to await all those promises which you can do by using Promise.all(). Promise.all() returns a Promise which will resolve when all Promises in the array passed to Promise.all() are settled. If you await that your children array will be propagated as you expect it to.

Here is your code with using Promise.all(). Because I don't have a suitable database ready at the moment I replaced all your asynchronous calls to the database with an asynchronous call to a function which has an artificial delay built-in so you can see how to actually await those and that the result is actually awaited.

const data = [
  {
    id: 1,
    task: "Clean apartment",
    completed: 0,
    parentid: null,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
  {
    id: 2,
    task: "Clean bathroom",
    completed: 0,
    parentid: 1,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
  {
    id: 3,
    task: "Clean kitchen",
    completed: 0,
    parentid: 1,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
  {
    id: 4,
    task: "Wash shower",
    completed: 0,
    parentid: 2,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
  {
    id: 5,
    task: "Wash toilet",
    completed: 0,
    parentid: 2,
    createdby: 1,
    createDate: "2022-03-24 00:47:33",
  },
  {
    id: 6,
    task: "Clean glass panes",
    completed: 1,
    parentid: 4,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
  {
    id: 7,
    task: "Clean faucet",
    completed: 0,
    parentid: 4,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
  {
    id: 8,
    task: "Clean sink",
    completed: 0,
    parentid: 3,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
  {
    id: 9,
    task: "Take out trash",
    completed: 1,
    parentid: 3,
    createdby: 1,
    createdat: "2022-03-24 00:47:33",
  },
];

async function comp(tasks, taskId) {
  // do your DB calls here (here just imitating the delay but the function are async to the result will remain the same)
  var task = await queryFind(tasks, taskId);
  var children = await queryFilter(tasks, taskId);

  // map() returns an array of promises as comp() returns a promise
  // Promise.all() returns a Promise that returns when all promises within the array are settled
  task.children = await Promise.all(
    children.map((child) => comp(tasks, child.id))
  );

  return task;
}

// this function immitates an async DB access.
async function queryFind(tasks, taskId) {
  // wait for 100 milliseconds (imitate delay)
  await sleep(100);
  return tasks.find((task) => task.id === taskId);
}

// this function immitates an async DB access.
async function queryFilter(tasks, taskId) {
  // wait for 100 milliseconds (imitate delay)
  await sleep(100);
  return tasks.filter((t) => t.parentid === taskId);
}

// delay execution. should imitage network delay here
async function sleep(ms) {
  return new Promise((resolve) => setTimeout(() => resolve(), ms));
}

// Start at task with ID 1; need to wrap the function call in an async method to be able to use await
(async () => {
  const test = await comp(data, 1);
  console.log(JSON.stringify(test, null, 4));
})();

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