Iterates over all own properties of an object, running a callback for each one.

  • Use Object.keys(obj) to get all the properties of the object.
  • Use Array.prototype.forEach() to run the provided function for each key-value pair.
  • The callback receives three arguments - the value, the key and the object.
const forOwn = (obj, fn) =>
  Object.keys(obj).forEach(key => fn(obj[key], key, obj));
forOwn({ foo: 'bar', a: 1 }, v => console.log(v)); // 'bar', 1