When modifying a value, return a clone. Doesn't modify the reference.

• When you change a value, always return a new instance
• Very Small (less than 3kb)
• Low-level (provides primitives, objects and arrays)

immutable-js provides high-level classes like Map, List, etc. Sheepable provides more low-level access.

Any Sheepable instance has a change method to change a value:

var pri = new Sheepable.Primitive('hello');
console.log(pri.value); //< "hello"
var newPri = pri.change('goodbye');
console.log(newPri.value); //< "goodbye"
console.log(pri.value); //< "hello"