composeMixins.js

const composeMixins = (...fns) => (
  obj = {},
  piped = x => fns.reduce((o, fn) => fn(o), x)
) => piped(obj);

const user = {
  name: 'kos',
  email: 'test@test.com',
};

const nameTrait = obj => ({ ...obj, getName: () => obj.name });
const emailTrait = obj => ({ ...obj, getEmail: () => obj.email });

const mixins = composeMixins(nameTrait, emailTrait);

const newUser = mixins(user);

console.log(newUser.getName()); // kos
console.log(newUser.getEmail()); // test@test.com

Here's a slightly better version:

const composeMixins = (...mixins) => (
  instance = {},
  mix = (...fns) => x => fns.reduce((acc, fn) => fn(acc), x)
) => mix(...mixins)(instance);

Note that you can customize the mixing behavior. For example, if you want to compose with first-in precedence instead of last-in:

const a = (instance) => Object.assign(instance, {
  foo: 1
});

const b = (instance) => Object.assign(instance, {
  foo: 2
});

const c1 = composeMixins(a, b);
const compose = (...fns) => x => fns.reduceRight((acc, fn) => fn(acc), x);

const r1 = c1({}); // {foo: 2}
const r2 = c1({}, compose); // {foo: 1}

@ericelliott that's helpful, thanks!