Flatten a nested objects to one dimensional array javascript

Question

I have a nested objects in this structure:

myArray = {
  "D": {
    "U": {
      "A300": "B300",
      "A326": "B326",
      "A344": "B344",
      "A345": "B345"
    },
    "P": {
      "A664": "B664",
      "A756": "B756"
    }
  },
  "I": {
    "U": {
      "A300": "B300",
      "A326": "B326"
    },
    "P": {
      "A756": "B756"
    }
  }
};

I am trying to get the data out of it to be only one dimensional (Flatten). I tried the code below but it doesn't work:

var myNewArray = [].concat.apply([], myArray);

and

var myNewArray = myArray.reduce(function(prev, curr) {
  return prev.concat(curr);
});

I want myNewArray to have ["B300","B326","B344","B345","B664","B756"]

Second answer: https://stackoverflow.com/questions/10865025/merge-flatten-an-array-of-arrays-in-javascript — Dzienny, Nov 21 '17 at 00:52
Already tried that and it gives an error about the reduce function — SMH, Nov 21 '17 at 00:54
@Andy Doesn't work if the elements aren't all in `myArray[0][0][0]`: https://jsfiddle.net/barmar/ryfwudqd/2/ — Barmar, Nov 21 '17 at 00:57
edited the question as it is an array of objects but it ends with an string which I want to get — SMH, Nov 21 '17 at 00:58
@SMH, if you had an array of objects, the first key would be numerical... — JJJ, Nov 21 '17 at 00:58

Titus · Accepted Answer · 2017-11-21T01:49:54.860

2

You can do something like this:

var myArray = [];
myArray[0] = [];
myArray[0][0] = [];
myArray[0][0][0] = [];
myArray[0][0][1] = [];
myArray[0][1] = [];
myArray[0][1][0] = [];

myArray[0][0][0][0] = "abc1";
myArray[0][0][0][1] = "abc2";
myArray[0][0][1][0] = "abc3";
myArray[0][1][0][1] = "abc4";
myArray[0][1][0][1] = "abc5";


function flat(acc, val){
  if(Array.isArray(val)){
     acc = acc.concat(val.reduce(flat, []));
  }else{
   acc.push(val);
  }
  return acc;
}

var newMyArray = myArray.reduce(flat, []);
console.log(newMyArray);

What this does is to recursively reduce all the inner values that are arrays.

It seems that you're dealing with an object. The previous title of your question and the name of the variable are misleading.

In any case, flattening an object is a very similar process.

var myArray = {"D":{"U":{"A300":"B300","A326":"B326","A344":"B344","A345":"B345"},"P":{"A664":"B664","A756":"B756"}},"I":{"U":{"A300":"B300","A326":"B326"},"P":{"A756":"B756"}}};

function flatObj(obj){
   return Object.keys(obj).reduce(function(acc, key){
     if(typeof obj[key] === "object"){
        acc = acc.concat(flatObj(obj[key]));
     }else{
        acc.push(obj[key]);
     }
     return acc;
   }, []);
}


var newMyArray = flatObj(myArray);
console.log(newMyArray);

edited Nov 21 '17 at 01:49

answered Nov 21 '17 at 00:59

Titus

22,031
1
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33

Looks nice, except he's changed the question to an array of objects, not array of arrays. – Barmar Nov 21 '17 at 01:02
@SMH I've edited my answer to make to add an example for flattening an object. – Titus Nov 21 '17 at 01:28
@Barmar I've saw that, I've edited my answer to address it. – Titus Nov 21 '17 at 01:29
Might need a unique filter also based on expected results shown. OP needs to clarify – charlietfl Nov 21 '17 at 01:34
@charlietfl Yes, they seem to be sorted in ascending order. – Titus Nov 21 '17 at 01:39
@SMH Do you want the resulting array to be sorted in any way ? – Titus Nov 21 '17 at 01:40
it doesn't matter but it gives an error: ReferenceError: invalid assignment left-hand side – SMH Nov 21 '17 at 01:41
@SMH my snipped seems to work, you probably have an error, something like `if(a = b && c = d)` (using `=` instead of `==`) – Titus Nov 21 '17 at 01:43
its not happy with => – SMH Nov 21 '17 at 01:45
@SMH Oh, that is just an arrow function, you can replace it with a normal function (eg: `function(acc, key){.....}`) – Titus Nov 21 '17 at 01:47
could you please edit it as I dont know what shall I do ? – SMH Nov 21 '17 at 01:49

score 2 · Answer 2 · answered Nov 21 '17 at 02:22

I just wanted to add my 2 cents since I was following this question and working on an answer before I left work. I'm home now so I want to post what I came up with.

const obj = {
  x1: { 
    y1: {
      z1: {
          h1: 'abc',
          h2: 'def'
          },
      z2: {
          h1: 123,
          h2: 456
         }
        }
  }
}

const valAll = getPropValuesAll(obj)
console.log(valAll)

function getPropValuesAll(obj, result = []){
  for(let k in obj){
    if(typeof obj[k] !== 'object'){
     result.push(obj[k])
        continue
    }
    getPropValuesAll(obj[k], result)
  }
  return result
}

sapics · Answer 3 · 2017-11-21T01:11:33.877

It would be easy and safe answer.

var myArray = [["abc1"],[["abc2",,"abc3"]],"abc4",{"r5": "abc5", "r6": "abc6"}];
var myNewArray = [];
function flatten(arr){
  if(Array.isArray(arr)){
    for(var i = 0, l = arr.length; i < l; ++i){
      if(arr[i] !== undefined){
        flatten(arr[i])
      }
    }
  } else if (typeof arr === 'object') {
    for(var key in arr){
      if(arr.hasOwnProperty(key)){
        flatten(arr[key])
      }
    }
  } else {
    myNewArray.push(arr)
  }
}
flatten(myArray)

console.log(myNewArray)

Flatten a nested objects to one dimensional array javascript

3 Answers3