Checking if a nested object contains only single key-value pair in javascript

Question

I want to check if a deeply nested object consists of single key-value pair, if it does, it should return true else false.

For e.g., I want the below code to return true,

var test = {
              level1:
                {
                  level2:
                     {
                       level3:'level3'
                     }
                } 
            };

And the below code to return false,

var test2 = {
                level1: {
                  level2: {'a': '1', 'b': 2},
                  level3: {'a': '2', 'c': 4}
                }
            };

Also, the below code should return true,

var test3 = 
{
  level1: {
    level2: {
      level3: {
        level4: {
          1: "1",
          2: "2",
          3: "3",
          4: "4"
        }
      }
    }
  }
}

I made the following program for it, but it doesn't work,

function checkNested(obj) {
  if(typeof(obj) === 'object') {
    if(Object.keys(obj).length === 1) {
      var key = Object.keys(obj);
      checkNested(obj[key])
    } else { 
      return(false);
    }
  }
  return(true);
}

Could someone please suggest me how can I achieve it?

CertainPerformance · Accepted Answer · 2019-01-21 09:54:22Z

4

With var key = Object.keys(obj);, key becomes an array (containing the one key), so obj[key] doesn't make sense. You might destructure the [key] instead:

const [key] = Object.keys(obj);
return checkNested(obj[key])

(make sure to return the recursive call)

Or, even better, use Object.values, since you don't actually care about the keys:

var test = {
  level1: {
    level2: {
      level3: 'level3'
    }
  }
};

var test2 = {
  level1: {
    level2: 'level2',
    level3: 'level3'
  }
};

function checkNested(obj) {
  if (typeof(obj) === 'object') {
    const values = Object.values(obj);
    if (values.length !== 1) {
      return false;
    }
    return checkNested(values[0]);
  }
  return true;
}

console.log(checkNested(test));
console.log(checkNested(test2));

answered Jan 21, 2019 at 9:54

CertainPerformance

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10 Comments

Frosted Cupcake Over a year ago

Your code is returning false for the below code, var test3 = { level1: { level2: { level3: { level4: { 1: "1", 2: "2", 3: "3", 4: "4" } } } } }

CertainPerformance Over a year ago

Yep, because it has more than one nested key-value pair.

Frosted Cupcake Over a year ago

Hi, I updated my question, I want the code to return true even for test3

CertainPerformance Over a year ago

It does return false for test3. (as your first comment noted)

Frosted Cupcake Over a year ago

My bad, I want it to return true even in such cases as test3

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