30-seconds-of-code/snippets/hasKey.md

title, tags

title	tags
hasKey	object,recursion,intermediate

Returns true if the target value exists in a JSON object, false otherwise.

Check if the key contains ., use String.prototype.split('.')[0] to get the first part and store as _key. Use typeof to check if the contents of obj[key] are an object and, if so, call hasKey with that object and the remainder of the key. Otherwise, use Object.keys(obj) in combination with Array.prototype.includes() to check if the given key exists.

const hasKey = (obj, key) => {
  if (key.includes('.')) {
    let _key = key.split('.')[0];
    if (typeof obj[_key] === 'object') return hasKey(obj[_key], key.slice(key.indexOf('.') + 1));
  }
  return Object.keys(obj).includes(key);
};

let obj = {
  a: 1,
  b: { c: 4 },
  'd.e': 5
};
hasKey(obj, 'a'); // true
hasKey(obj, 'b'); // true
hasKey(obj, 'b.c'); // true
hasKey(obj, 'd.e'); // true
hasKey(obj, 'd'); // false
hasKey(obj, 'f'); // false