I need a simple method to get the key of a nested object, e.g. description. This is my structure:

let data = [
  {
    name: "Apple",
    id: 1,
    alt: [{ name: "fruit1", description: "tbd1" }]
  },
  {
    name: "Banana",
    id: 2,
    alt: [{ name: "fruit2", description: "tbd2" }]
  },
  {
    name: "Blueberry",
    id: 3,
    alt: [{ name: "fruit3", description: "tbd3" }]
  }
];

I need a simple method to get the key of a nested object, e.g. description. This is my structure:

let data = [
  {
    name: "Apple",
    id: 1,
    alt: [{ name: "fruit1", description: "tbd1" }]
  },
  {
    name: "Banana",
    id: 2,
    alt: [{ name: "fruit2", description: "tbd2" }]
  },
  {
    name: "Blueberry",
    id: 3,
    alt: [{ name: "fruit3", description: "tbd3" }]
  }
];

• javascript
• reactjs

• 1 what you've tried so far ? what is desired output ? please post the related code – Code Maniac Commented Oct 29, 2019 at 11:49
• In this particular case, Object.keys(data[0].alt[0]) is ["name", "description"], and the order of that keys array isn't guaranteed. If you meant to ask how to get the value: data[0].alt[0].description is tbd1 – user5734311 Commented Oct 29, 2019 at 11:52
• 1 Get the key, or the value? – Mr. Polywhirl Commented Oct 29, 2019 at 11:52
• Do you want to get a single key or want all the descriptions in array? – pradeepchauhan_pc Commented Oct 29, 2019 at 12:38

4 Answers 4

You can use Object.keys(x) to list the keys for any arbitrary object. Regarding the nesting, it is just a case of knowing which of the nested indicies you wish to list fields for and supplying it.

You might want to consider something like this

If you want the keys, including nested keys, you can recursively traverse the array/objects like so.

There are two optional parameters that allow you to:

• Ignore the array part i.e. skipArrays
• Whether to keep the parent object keys i.e. keepObjKeys.

const isObject = (obj) => obj != null && obj.constructor.name === "Object";

let data = [
  { name: "Apple",     id: 1, alt: [{ name: "fruit1", description: "tbd1" }] },
  { name: "Banana",    id: 2, alt: [{ name: "fruit2", description: "tbd2" }] },
  { name: "Blueberry", id: 3, alt: [{ name: "fruit3", description: "tbd3" }] }
];

console.log(getKeys(data, false, false));
console.log(getKeys(data, true, true));

function getKeys(obj, keepObjKeys, skipArrays, keys=[], scope=[]) {
  if (Array.isArray(obj)) {
    if (!skipArrays) scope.push('[' + obj.length + ']');
    obj.forEach((o) => getKeys(o, keepObjKeys, skipArrays, keys, scope), keys);
  } else if (isObject(obj)) {
    Object.keys(obj).forEach((k) => {
      if ((!Array.isArray(obj[k]) && !isObject(obj[k])) || keepObjKeys) {
        let path = scope.concat(k).join('.').replace(/\.\[/g, '[');
        if (!keys.includes(path)) keys.push(path);
      }
      getKeys(obj[k], keepObjKeys, skipArrays, keys, scope.concat(k));
    }, keys);
  }
  return keys;
}

.as-console-wrapper { top: 0; max-height: 100% !important; }

To get the keys of a nested object:

Object.keys(data[0].alt[0]) => results in string array ["name","description"] - not neccessarily in this order.

To get value of description key:

data[0].alt[0].description => results in tbd1 string.

To get an array of all descriptions:

data.map(obj => obj.alt[0].description).

Didn't know what you meant, so gave you all the options I could think of.

May help you

let keys = Object.keys(yourObject);

keys array contains name,description