Return an array of objects from a recursive function in Javascript

Question

I'm working on recursive functions.

I must push all objects that have the key "data: true" in an array. The console.log in the middle of my function gives me all those objects in separate arrays.

But I can't return an array with the objects at the end. What am I doing wrong? Thanks

const entries = {
  root: {
    data: true,
    key: "root",
    text: "some text"
  },
  test: {
    one: {
      two: {
        data: true,
        key: "test.one.two",
        text: "some text.again"
      },
      three: {
        data: true,
        key: "test.one.three",
        text: "some.more.text"
      }
    },
    other: {
      data: true,
      key: "test3",
      text: "sometext.text"
    }
  },
  a: {
    b: {
      data: true,
      key: "a.b",
      text: "a.b.text"
    },
    c: {
      d: {
        data: true,
        key: "a.c.d",
        text: "some.a.c.d"
      }
    }
  }
};


function recursiveFunc(data) {
  let tab = [];
  for (let property in data) {
    if (data.hasOwnProperty(property)) {
      if (data[property].data === true) {
        tab.push(data[property]);
        console.log("t", tab);
      } else {
        recursiveFunc(data[property])
      }
    }
  }
  return tab
}

console.log(recursiveFunc(entries));

You are never using the result of the recursive calls. Just assign it to something and push it to the original array (or concat it, or whatever): jsfiddle.net/aco2qryn — briosheje
– briosheje, Commented Nov 22, 2018 at 10:49
Thanks a lot briosheje, it works now. I had tried something like this but forgot the spread operator. — Charlote22
– Charlote22, Commented Nov 22, 2018 at 10:55
None of the answers corrected the infinite recursion when data is false. — Zim
– Zim, Commented Nov 22, 2018 at 11:00
@Zim that's not true, my fiddle above works with false as a parameter as well. There is no infinite recursion in that case. — briosheje
– briosheje, Commented Nov 22, 2018 at 11:15

osiris85 · Accepted Answer · 2018-11-22 10:49:23Z

7

Add tab.concat() on the recursive call for join the items returned by the recursive fn.

const entries = {
  root: {
    data: true,
    key: "root",
    text: "some text"
  },
  test: {
    one: {
      two: {
        data: true,
        key: "test.one.two",
        text: "some text.again"
      },
      three: {
        data: true,
        key: "test.one.three",
        text: "some.more.text"
      }
    },
    other: {
      data: true,
      key: "test3",
      text: "sometext.text"
    }
  },
  a: {
    b: {
      data: true,
      key: "a.b",
      text: "a.b.text"
    },
    c: {
      d: {
        data: true,
        key: "a.c.d",
        text: "some.a.c.d"
      }
    }
  }
};


function recursiveFunc(data) {
  let tab = [];
  for (let property in data) {
    if (data.hasOwnProperty(property)) {
      if (data[property].data === true) {
        tab.push(data[property]);
        console.log("t", tab);
      } else { 
        tab = tab.concat(recursiveFunc(data[property]));
      }
    } 
  } 
  return tab
}
console.log(recursiveFunc(entries));

answered Nov 22, 2018 at 10:49

osiris85

2061 silver badge7 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Zim Over a year ago

Infinite recursion when there is a data = false. See corrected answer: stackoverflow.com/a/53429407/2898738

Zim · Accepted Answer · 2018-11-22 11:01:50Z

1

You can pass an array as second argument that will act as an accumulator.

Plus, I fixed your function that loops infinitely when data = false:

function recursiveFunc(data, acc) {
  for (let property in data) {
    if (data.hasOwnProperty(property) && typeof data[property] === "object") {

      var current = data[property];

      if (current.data === true) {
        acc.push(current);
      } else {
        recursiveFunc(current, acc)
      }

    }
  }
}

Usage:

var results = [];
recursiveFunc(entries, results);
console.log(results);

edited Nov 22, 2018 at 11:01

answered Nov 22, 2018 at 10:56

Zim

1,4831 gold badge10 silver badges21 bronze badges

Comments

Marius · Accepted Answer · 2018-11-22 11:04:29Z

0

You could use a global variable.

const entries = { ... };


var tab = [];

function getTab(data) {
    tab = [];
    recursiveFunc(data);
    return tab;
}
function recursiveFunc(data) {
  for (let property in data) {
    if (data.hasOwnProperty(property) && typeof data[property] === "object") {
      if (data[property].data === true) {
        tab.push(data[property]);
      } else {
        recursiveFunc(data[property])
      }
    }
  }
}

getTab(entries);

answered Nov 22, 2018 at 11:04

Marius

1,6141 gold badge12 silver badges20 bronze badges

Collectives™ on Stack Overflow

Return an array of objects from a recursive function in Javascript

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related