hasKey

JavaScript, Object

Checks if the target value exists in a JSON object.

  • Check if keys is non-empty and use Array.prototype.every() to sequentially check its keys to internal depth of the object, obj.
  • Use Object.prototype.hasOwnProperty() to check if obj does not have the current key or is not an object, stop propagation and return false.
  • Otherwise assign the key's value to obj to use on the next iteration.
  • Return false beforehand if given key list is empty.
const hasKey = (obj, keys) => {
  return (
    keys.length > 0 &&
    keys.every(key => {
      if (typeof obj !== 'object' || !obj.hasOwnProperty(key)) return false;
      obj = obj[key];
      return true;
    })
  );
};
let obj = {
  a: 1,
  b: { c: 4 },
  'b.d': 5
};
hasKey(obj, ['a']); // true
hasKey(obj, ['b']); // true
hasKey(obj, ['b', 'c']); // true
hasKey(obj, ['b.d']); // true
hasKey(obj, ['d']); // false
hasKey(obj, ['c']); // false
hasKey(obj, ['b', 'f']); // false

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