deep flatten all items in collection using lodash

Question

I'm looking to flatten an array that look like this:

[{
    "id": 0,
    "text": "item 0"
}, {
    "id": 1,
    "items": [{
        "id": 2,
        "text": "item 2"
    }, {
        "id": 3,
        "items": [{
            "id": 4,
            "text": "item 4"
        }]
    }]
}]

into this

[{
    "id": 0,
    "text": "item 0"
}, {
    "id": 2,
    "text": "item 2"
}, {
    "id": 4,
    "text": "item 4"
}]

basically keeping all element that doesn't have an "items" property, and if they have one, recursively traverse all "items" arrays deep.

I could indeed write a recursive function, but I'm looking for a nice looking lodash or underscore way to solve this.

Answer 1

There is no neat function for this in lodash or underscore. I think a recursive function is your best bet:

function collect(array, result) {
  array.forEach(function(el) {
    if(el.items) {
      collect(el.items, result);
    } else {
      result.push(el);
    }
  });
}

var array = [{
    "id": 0,
    "text": "item 0"
}, {
    "id": 1,
    "items": [{
        "id": 2,
        "text": "item 2"
    }, {
        "id": 3,
        "items": [{
            "id": 4,
            "text": "item 4"
        }]
    }]
}];

function collect(array, result) {
  array.forEach(function(el) {
    if(el.items) {
      collect(el.items, result);
    } else {
      result.push(el);
    }
  });
}
var result = [];
collect(array, result);
console.log(result);