Looping through a nested object and imputed missed keys

Question

I'm new to javascript and trying to loop through a nested object to insert a missing key at the second level where I would like to add any missing keys below 5 and assign them a value of zero. So if we have keys 5 and 3, I would like to add 4, 2, and 1 keys with a value of zero.

'''0:{"key": "2010", "values": [ { "key": "4", "value": 10 }, { "key": "3", "value": 2 } ]}

1:{"key": "2011", "values": [ { "key": "5", "value": 25 }, { "key": "3", "value": 4 } ]}'''

Answer 1

You need to map over the existing data and check to see if the key exists already, hope this helps you understand what's happening.

let data = [
  {
    key: "2010",
    values: [
      { key: "4", value: 10 },
      { key: "3", value: 2 },
    ],
  },
  {
    key: "2011",
    values: [
      { key: "5", value: 25 },
      { key: "3", value: 4 },
    ],
  },
];

data = data.map((currentItem) => {
    
  // Create a new temp values array
  const newValues = [];

  // Ensure all keys are present (between 1 and 5)
  for (let i = 1; i <= 5; i++) {

    // Check to see if the key already exists
    const existingValue = currentItem.values.find(({ key }) => key === String(i));

    // Insert the existing value or initialise the key to 0
    newValues.push({ key: String(i), value: existingValue ? existingValue.value : 0 });
  }

  // Return the new object, replacing the values array with the new one
  return { ...currentItem, values: newValues };
});