Loop over each element in Object Arrays

Question

I've an Object containing data that looks like this,

obj = {
Q1:['val1','val2'],
Q2:['val3','val4','val5'],
Q3:['val8']
}

I was trying to loop over keys and get and first element in each key concate each element in each array, and join them together using , (my object has more keys that this ofc)

So the output should be like

val1,val3,val8
val2,val4,
,val5,

I tried to loop over keys and getting each value but i think i'm missing something in my loop, as i can't change the key if it found element in each object

These are my trials below.

for (var key in obj) {
  if (obj.hasOwnProperty(key)) {
    for (let i = 0; i < obj[key].length; i++) {
          console.log(obj[key][i])//This is always looping on the same key but different element          
    }
  }
}

while i want it to be something close to

 for (var key in obj) {
  if (obj.hasOwnProperty(key)) {
          console.log(obj[key][i])         
  }
}

would you please clear more about the output description you mentioned? — Shuvojit Saha, Jun 24 '20 at 10:35
I want to concatenate each element from each array, as i should get val1 concat val3 concat val8 , then i'll make string join between them using , in order to make then val1,val3,val8 .... and whenever it doesn't find a value inside this array (as not all arrays are equal it should put just blank and do a , so it become val2,val4,'' — Doom, Jun 24 '20 at 10:39
@user120242 this is talking about equal length arrays, but unfortunately this isn't my case — Doom, Jun 24 '20 at 10:55
Scroll down. To emulate zip it also has to support unequal length arrays. — user120242, Jun 24 '20 at 10:57
Or are you talking about [cartesian](https://stackoverflow.com/questions/12303989/cartesian-product-of-multiple-arrays-in-javascript)? Your output actually doesn't make sense. — user120242, Jun 24 '20 at 11:02
I'm trying to put my output in this form in-order when i write it to csv file, it should be column row wise, but each complete row, have a value from each column. (if my explanation is not clear please tell me ) so the final goal for me to have an [ [ ] ] , where each array inside the big array, should contain the output as above to be written to csv — Doom, Jun 24 '20 at 11:06
@AdhamNawito val3 is column 1, val5 is column 3. Those are different columns, and from the same row? — user120242, Jun 24 '20 at 11:06

score 0 · Answer 1 · answered Jun 24 '20 at 10:43

My solution uses a deep copy of the object and then a recursive array manipulation via shift():

obj = {
  Q1:['val1','val2'],
  Q2:['val3','val4','val5'],
  Q3:['val8']
}

var resObj = [];

function printByIndex(obj){
  var newObj = JSON.parse(JSON.stringify(obj));
  printByIndexHelper(newObj, 0);
}

function printByIndexHelper(obj, i){
  var flag = false;
  resObj[i] = [];
  Object.keys(obj).forEach(function(key){
    if(obj[key].length > 0){
      resObj[i].push(obj[key].shift());
      if(obj[key].length > 0){
        flag = true;
      }
    }else{
     resObj[i].push(null);
     }
  });
  if(flag){
    printByIndexHelper(obj, i+1);
  }
}

printByIndex(obj);
console.log(resObj);

Satya Rajbhar · Answer 2 · 2020-06-24T11:44:52.147

0

check this same output as u require

 obj = {
    Q1:['val1','val2'],
    Q2:['val3','val4','val5'],
    Q3:['val8']
    }
    
    var keys = Object.keys(obj);
    var stack = [];
    var maxLength = getMaxLength(obj);
    
      for(var k = 0; k < 3;k ++) {
          var arr = [];
        
        for(var i = 0; i<keys.length;i++) {
          const key = keys[i];
          const elements = obj[key];
    
            if(k < elements.length) {
              arr.push(elements[k]);  
            }
        }
    
            console.log(arr+"\n");
        //stack.push(arr);
    }
    
    
    function getMaxLength(jsonObj) {
      var max;
      var jsonKeys = Object.keys(jsonObj);
      for(var key of jsonKeys) {
        const arr = jsonObj[key];
        if (max == null || arr.length > max) {
          max = arr.length;  
        } 
      }
      return max;
    }

edited Jun 24 '20 at 11:44

answered Jun 24 '20 at 10:52

Satya Rajbhar

21
5

would you explain it a little bit ? – Doom Jun 24 '20 at 10:56
1. get keys from object in array var objArray = Object.keys(obj) 2.get keys array (var key of objArray) 3.join array in string var str = elements.join(","); – Satya Rajbhar Jun 24 '20 at 11:00
1

This just joins each value array – adiga Jun 24 '20 at 11:02
[How do I create a runnable stack snippet?](https://meta.stackoverflow.com/questions/358992) – adiga Jun 24 '20 at 11:02
@adiga i provide answer according requirement what do you want – Satya Rajbhar Jun 24 '20 at 11:09
2

The answer is not according to OP's requirement – adiga Jun 24 '20 at 11:09
@adiga yes you are right. Now i understand the requirement – Satya Rajbhar Jun 24 '20 at 11:16
@AdhamNawito now you can check it is working – Satya Rajbhar Jun 24 '20 at 11:49
@SatyaRajbhar , this doesn't solve my exact problem .. but it helped me to find a solution. Thank you for your help. – Doom Jun 25 '20 at 18:07

score 0 · Answer 3 · answered Jun 24 '20 at 10:59

Maps over arrays and joins string. Math.max to get full length to iterate over. Uses flatMap to filter out unequal length array values.

obj = {
Q1:['val1','val2'],
Q2:['val3','val4','val5'],
Q3:['val8']
}

const o = Object.values(obj)
const len = Math.max(...o.map(({length})=>length))
console.log(
Array(len).fill().map((x,i)=>o.flatMap(q=>q[i]||[]).join(','))
)

Loop over each element in Object Arrays

3 Answers3