forOwn

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