Validate the properties of a JavaScript object

Checking the shape of a JavaScript object is fairly common, especially as part of a validation process. Using JavaScript's built-in methods and APIs, you can easily validate the properties of an object against an array of keys or another object to ensure they match.

Validate against an array of keys

Given an array of keys, you can use Object.keys() to compare the keys of an object to the specified array. This will ensure that the object contains only the keys specified in the array.

Depending on your needs, you can loosely check if the object keys exactly match the array or if they are a subset or superset of the array. All you need to use is Array.prototype.every() and Array.prototype.includes() to perform the checks.

// All keys in the object are present in the specified array.
const keysAreValid = (obj, keys) =>
  Object.keys(obj).every(key => keys.includes(key));

// All keys in the specified array are present in the object.
const allKeysArePresent = (obj, keys) => {
  const objKeys = Object.keys(obj);
  return keys.every(key => objKeys.includes(key));
};

// Check if the keys of an object match the specified array.
const keysMatch = (obj, keys) =>
  keysAreValid(obj, keys) && allKeysArePresent(obj, keys);

const obj = { id: 1, name: 'apple', price: 1.2 };
const keys = ['id', 'name', 'price'];

keysAreValid(obj, keys); // true
keysAreValid(obj, [...keys, 'quantity']); // true

allKeysArePresent(obj, keys); // true
allKeysArePresent(obj, [...keys, 'quantity']); // false

keysMatch(obj, keys); // true
keysMatch(obj, [...keys, 'quantity']); // false

Validate against another object

If you want to validate an object against another object, you simply need to retrieve the keys of the second object, using Object.keys(), and compare them to the keys of the first object. The rest of the process is the same as the previous example.

const keysAreValid = (obj, keys) =>
  Object.keys(obj).every(key => keys.includes(key));

const allKeysArePresent = (obj, keys) => {
  const objKeys = Object.keys(obj);
  return keys.every(key => objKeys.includes(key));
};

const keysMatch = (obj, keys) =>
  keysAreValid(obj, keys) && allKeysArePresent(obj, keys);

// All keys in the target object are present in the source object.
const objectKeysAreValid = (obj, source) =>
  keysAreValid(obj, Object.keys(source));

// All keys in the source object are present in the target object.
const objectKeysArePresent = (obj, source) =>
  allKeysArePresent(obj, Object.keys(source));

// Check if the keys of the target object match the source object.
const objectKeysMatch = (obj, source) =>
  keysMatch(obj, Object.keys(source));

const target = { id: 1, name: 'apple', price: 1.2 };
const source = { id: 1, name: 'apple', price: 1.2 };

objectKeysAreValid(target, source); // true
objectKeysAreValid(target, { ...source, quantity: 10 }); // true

objectKeysArePresent(target, source); // true
objectKeysArePresent(target, { ...source, quantity: 10 }); // false

objectKeysMatch(target, source); // true
objectKeysMatch(target, { ...source, quantity: 10 }); // false