Derivative

This librairy expose two kinds of objects types: mutables and derivatives. Mutables hold a current immutable value. Their current value can be replaced, that's why it's called a mutable. Derivatives are values derived from one or more mutables or other derivatives (their source values). Each derivative have a function that describe their relationship to their source values and they will always maintain that relationship true, even if their source value change.

Example of what you can do

const numberA = new MutableNumber(2);
const numberB = new MutableNumber(3);

const sum = numberA.add(numberB);

console.log('sum:', sum.get());
// sum: 5

numberA.set(7);

console.log('sum:', sum.get());
// sum: 10

// sum will always be the sum of the 2 other numbers, even when the two numbers change.

Another sum example using a list

const numbers = new MutableList([1, 2, 3, 4]);

const sum = numbers.reduce((sum, number) => sum + number, 0);

console.log('sum:', sum.get());
// sum: 10

// pushing a new number in the list
numbers.push(5);

console.log('sum:', sum.get());
// sum: 15