If you only want to combine own-properties, use extend-shallow.
var mixin = require('{%= name %}');
var obj = {c: 'c'};
var foo = mixin({a: 'a'}, {b: 'b'});
console.log(foo);
//=> {c: 'c', a: 'a', b: 'b'}
console.log(obj);
//=> {c: 'c'}
mixin({}, {a: 'a'}, {b: 'b'});
//=> {a: 'a', b: 'b'}