Deep Flatten JavaScript Object Recursively

Question

Data:

var data = [
    {
      "id": 1,
      "level": "1",
      "text": "Sammy",
      "type": "Item",
      "items": [
        {
          "id": 11,
          "level": "2",
          "text": "Table",
          "type": "Item",
          "items": [
            {
              "id": 111,
              "level": "3",
              "text": "Dog",
              "type": "Item",
              "items": null
            },
            {
              "id": 112,
              "level": "3",
              "text": "Cat",
              "type": "Item",
              "items": null
            }
          ]
        },
        {
          "id": 12,
          "level": "2",
          "text": "Chair",
          "type": "Item",
          "items": [
            {
              "id": 121,
              "level": "3",
              "text": "Dog",
              "type": "Item",
              "items": null
            },
            {
              "id": 122,
              "level": "3",
              "text": "Cat",
              "type": "Item",
              "items": null
            }
          ]
        }
      ]
    },
    {
      "id": 2,
      "level": "1",
      "text": "Sundy",
      "type": "Item",
      "items": [
        {
          "id": 21,
          "level": "2",
          "text": "MTable",
          "type": "Item",
          "items": [
            {
              "id": 211,
              "level": "3",
              "text": "MTDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 212,
              "level": "3",
              "text": "MTCat",
              "type": "Item",
              "items": null
            }
          ]
        },
        {
          "id": 22,
          "level": "2",
          "text": "MChair",
          "type": "Item",
          "items": [
            {
              "id": 221,
              "level": "3",
              "text": "MCDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 222,
              "level": "3",
              "text": "MCCat",
              "type": "Item",
              "items": null
            }
          ]
        }
      ]
    },
    {
      "id": 3,
      "level": "1",
      "text": "Bruce",
      "type": "Folder",
      "items": [
        {
          "id": 31,
          "level": "2",
          "text": "BTable",
          "type": "Item",
          "items": [
            {
              "id": 311,
              "level": "3",
              "text": "BTDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 312,
              "level": "3",
              "text": "BTCat",
              "type": "Item",
              "items": null
            }
          ]
        },
        {
          "id": 32,
          "level": "2",
          "text": "Chair",
          "type": "Item",
          "items": [
            {
              "id": 321,
              "level": "3",
              "text": "BCDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 322,
              "level": "3",
              "text": "BCCat",
              "type": "Item",
              "items": null
            }
          ]
        }
      ]
    }
  ];

Code:

var fdr = [];
var fd = function(n) {
  if (n.items) {
    _.forEach(n.items, function (value){
      fd(value);
    });
  }

  fdr.push(n);
};
_.forEach(data, fd);
console.log(fdr);

Desired output:

var data = [
    {
      "id": 1,
      "level": "1",
      "text": "Sammy",
      "type": "Item",
      "items": []
    },
    {
      "id": 11,
      "level": "2",
      "text": "Table",
      "type": "Item",
      "items": []
    },
    {
      "id": 111,
      "level": "3",
      "text": "Dog",
      "type": "Item",
      "items": null
    },
    {
      "id": 112,
      "level": "3",
      "text": "Cat",
      "type": "Item",
      "items": null
    },
    {
      "id": 12,
      "level": "2",
      "text": "Chair",
      "type": "Item",
      "items": []
    },
    {
      "id": 121,
      "level": "3",
      "text": "Dog",
      "type": "Item",
      "items": null
    },
    {
      "id": 122,
      "level": "3",
      "text": "Cat",
      "type": "Item",
      "items": null
    },
    {
      "id": 2,
      "level": "1",
      "text": "Sundy",
      "type": "Item",
      "items": []
    },
    {
      "id": 21,
      "level": "2",
      "text": "MTable",
      "type": "Item",
      "items": []
    },
    {
      "id": 211,
      "level": "3",
      "text": "MTDog",
      "type": "Item",
      "items": null
    },
    {
      "id": 212,
      "level": "3",
      "text": "MTCat",
      "type": "Item",
      "items": null
    },
    {
      "id": 22,
      "level": "2",
      "text": "MChair",
      "type": "Item",
      "items": []
    },
    {
      "id": 221,
      "level": "3",
      "text": "MCDog",
      "type": "Item",
      "items": null
    },
    {
      "id": 222,
      "level": "3",
      "text": "MCCat",
      "type": "Item",
      "items": null
    },
    {
      "id": 3,
      "level": "1",
      "text": "Bruce",
      "type": "Folder",
      "items": []
    },
    {
      "id": 31,
      "level": "2",
      "text": "BTable",
      "type": "Item",
      "items": []
    },
    {
      "id": 311,
      "level": "3",
      "text": "BTDog",
      "type": "Item",
      "items": null
    },
    {
      "id": 312,
      "level": "3",
      "text": "BTCat",
      "type": "Item",
      "items": null
    },
    {
      "id": 32,
      "level": "2",
      "text": "Chair",
      "type": "Item",
      "items": []
    },
    {
      "id": 321,
      "level": "3",
      "text": "BCDog",
      "type": "Item",
      "items": null
    },
    {
      "id": 322,
      "level": "3",
      "text": "BCCat",
      "type": "Item",
      "items": null
    }
  ];

Conditions:

• Object have unknowns level. Some child item may have one level down and some could have up to 5.

Questions

The fd function in the code is what I have come up with. I believe there's a 'cleaner' way to do this, just can't think of something. Plus, the function return items object, render it circular object.

JsBin: http://jsbin.com/debojiqove/2/edit?html,js,output

Is there a way to flatten object recursively with lodash or just plain JavaScript?.

Answer 1

Here is my version of the recursive flattenItems function. Note that I have removed the items property at all levels in the final result.

function flattenItems(data) {
    // flat is the array that we will return by the end
    var flat = [];
    data.forEach(function(item) {
        // get child properties only
        var flatItem = {};
        Object.keys(item).forEach(function(key) {
            if(item[key] && item.hasOwnProperty(key) && !Array.isArray(item[key])) {
                flatItem[key] = item[key];
            }
            // recursive flattern on subitems
            // add recursive call results to the 
            // current stack version of "flat", by merging arrays
            else if(Array.isArray(item[key])) {
                Array.prototype.push.apply(flat, flattenItems(item[key]));
            }
        });
        flat.push(flatItem);
    });
    // sort by level before returning
    return flat.sort(function(i1, i2) {
        return parseInt(i1.level) - parseInt(i2.level);
    });
  }

Here is a fiddle using your sample data, check the console.

Answer 2

Since Lo-Dash 3.0.0, _.flattenDeep(data) will return a deeply flattened array as you desire. There is also a _.flatten(data) function that flattens shallowly.

Answer 3

Only a single liner function can do this job.

var data = [{ "id": 1, "level": "1", "text": "Sammy", "type": "Item", "items": [{ "id": 11, "level": "2", "text": "Table", "type": "Item", "items": [{ "id": 111, "level": "3", "text": "Dog", "type": "Item", "items": null }, { "id": 112, "level": "3", "text": "Cat", "type": "Item", "items": null }] }, { "id": 12, "level": "2", "text": "Chair", "type": "Item", "items": [{ "id": 121, "level": "3", "text": "Dog", "type": "Item", "items": null }, { "id": 122, "level": "3", "text": "Cat", "type": "Item", "items": null }] }] }, { "id": 2, "level": "1", "text": "Sundy", "type": "Item", "items": [{ "id": 21, "level": "2", "text": "MTable", "type": "Item", "items": [{ "id": 211, "level": "3", "text": "MTDog", "type": "Item", "items": null }, { "id": 212, "level": "3", "text": "MTCat", "type": "Item", "items": null }] }, { "id": 22, "level": "2", "text": "MChair", "type": "Item", "items": [{ "id": 221, "level": "3", "text": "MCDog", "type": "Item", "items": null }, { "id": 222, "level": "3", "text": "MCCat", "type": "Item", "items": null }] }] }, { "id": 3, "level": "1", "text": "Bruce", "type": "Folder", "items": [{ "id": 31, "level": "2", "text": "BTable", "type": "Item", "items": [{ "id": 311, "level": "3", "text": "BTDog", "type": "Item", "items": null }, { "id": 312, "level": "3", "text": "BTCat", "type": "Item", "items": null }] }, { "id": 32, "level": "2", "text": "Chair", "type": "Item", "items": [{ "id": 321, "level": "3", "text": "BCDog", "type": "Item", "items": null }, { "id": 322, "level": "3", "text": "BCCat", "type": "Item", "items": null }] }] }],

flatIron = (a,b) => a.reduce((p,c) => {!!c.items ? (p.push(c), flatIron(c.items,p), c.items = []) : p.push(c); return p},b),
 flatArr = flatIron(data,[]);

document.write('<pre>' + JSON.stringify(flatArr, 0, 2) + '</pre>');

Answer 4

A shorter solution using reduce and recursion

function flatten(data){
  return data.reduce(function(result,next){
    result.push(next);
    if(next.items){
      result = result.concat(flatten(next.items));  
      next.items = [];
    }
    return result;
  },[]);
}

var data = [
    {
      "id": 1,
      "level": "1",
      "text": "Sammy",
      "type": "Item",
      "items": [
        {
          "id": 11,
          "level": "2",
          "text": "Table",
          "type": "Item",
          "items": [
            {
              "id": 111,
              "level": "3",
              "text": "Dog",
              "type": "Item",
              "items": null
            },
            {
              "id": 112,
              "level": "3",
              "text": "Cat",
              "type": "Item",
              "items": null
            }
          ]
        },
        {
          "id": 12,
          "level": "2",
          "text": "Chair",
          "type": "Item",
          "items": [
            {
              "id": 121,
              "level": "3",
              "text": "Dog",
              "type": "Item",
              "items": null
            },
            {
              "id": 122,
              "level": "3",
              "text": "Cat",
              "type": "Item",
              "items": null
            }
          ]
        }
      ]
    },
    {
      "id": 2,
      "level": "1",
      "text": "Sundy",
      "type": "Item",
      "items": [
        {
          "id": 21,
          "level": "2",
          "text": "MTable",
          "type": "Item",
          "items": [
            {
              "id": 211,
              "level": "3",
              "text": "MTDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 212,
              "level": "3",
              "text": "MTCat",
              "type": "Item",
              "items": null
            }
          ]
        },
        {
          "id": 22,
          "level": "2",
          "text": "MChair",
          "type": "Item",
          "items": [
            {
              "id": 221,
              "level": "3",
              "text": "MCDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 222,
              "level": "3",
              "text": "MCCat",
              "type": "Item",
              "items": null
            }
          ]
        }
      ]
    },
    {
      "id": 3,
      "level": "1",
      "text": "Bruce",
      "type": "Folder",
      "items": [
        {
          "id": 31,
          "level": "2",
          "text": "BTable",
          "type": "Item",
          "items": [
            {
              "id": 311,
              "level": "3",
              "text": "BTDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 312,
              "level": "3",
              "text": "BTCat",
              "type": "Item",
              "items": null
            }
          ]
        },
        {
          "id": 32,
          "level": "2",
          "text": "Chair",
          "type": "Item",
          "items": [
            {
              "id": 321,
              "level": "3",
              "text": "BCDog",
              "type": "Item",
              "items": null
            },
            {
              "id": 322,
              "level": "3",
              "text": "BCCat",
              "type": "Item",
              "items": null
            }
          ]
        }
      ]
    }
  ];

var result = flatten(data);

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 5

With a bit of ES6 flavor

function flatten(xs) {
  return xs.reduce((acc, x) => {
    acc = acc.concat(x);
    if (x.items) {
      acc = acc.concat(flatten(x.items));
      x.items = [];
    }
    return acc;
  }, []);
}

Answer 6

Modified Роман Парадеев answer to make it somewhat more dynamic.

function flatten(xs, childSelector) {
  return xs.reduce((acc, x) => {
    acc = acc.concat(x);
    let children = childSelector(x);
    if (children) {
      acc = acc.concat(flatten(children, childSelector));
    }
    return acc;
  }, []);
}

Now items is not hardcoded, and you can use it flatten(data, x => x.items).