Alnico is a TypeScript library under development that investigates the potential benefits of
combining functional programming principles with the modularity strengths of object-oriented
programming. Inspired by concepts from functional programming, Alnico seeks to introduce a novel
approach to code structure and organization. It achieves this by eliminating the use of this and
new keywords in favor of composable states and methods bundled into single units.
npm i alnicoThis section explores the usage of Alnico through a practical example. The example implements a counter using Alnico's composition functionality:
import { compose } from 'alnico';
/**
* Alternatively:
* import alnico from 'alnico';
*
* alnico.compose( ... )
*/
const { incCount, resetCount, curCount } = compose<
{ count: number },
{ incCount: () => void; resetCount: () => void; curCount: () => number }
>(
{ count: 0 },
{
incCount: ({ count }) => {
count.set(count.get() + 1);
},
resetCount: ({ count }) => {
count.set(0);
},
curCount: ({ count }) => count.get(),
}
);
curCount(); //0;
incCount();
curCount(); //1;
incCount();
curCount(); //2;
incCount();
curCount(); //3;
resetCount();
curCount(); //0;To illustrate Alnico's composition approach, this example constructs a set of interrelated methods
using the compose function. These methods function independently, eliminating the need for a central
managing object. This is achieved by removing the this keyword and explicitly passing all internal
dependencies through the composer functions' parameters. This fosters a programming style with clear
and unambiguous dependency management. Additionally, TypeScript's IntelliSense functionality
enhances development by automatically suggesting parameters for each function.
It's important to note that Alnico's effectiveness is heavily dependent on TypeScript. The proposed Alnico composition approach wouldn't be as efficient with plain JavaScript. While it would still function, managing parameter requirements for composer functions and allowed parameters for dependency methods would become increasingly difficult, especially in complex use cases.
Alnico compositions consist of three parts, with one being optional. Let's examine them in detail:
-
State: This section defines the variables used within the composition. Each state variable is accessible as a dependency in a method composer function. When used as a dependency, each state variable behaves like a method bundle with three functions:
get,set, andexc. We'll explore these functions in more detail later. -
Methods composition: This is the core component of Alnico. It's responsible for producing the final methods as a result of the composition process. The source for these methods comes from the composers passed as the second argument. The key difference between composers and the methods they create is that composers have an extra parameter placed first, before the rest of the arguments accepted by the methods. This extra argument is the bundle that contains the dependencies as named properties.
Even the method itself can be included in the dependency bundle, allowing for recursion.
next({ next, mem }, p) { if (p <= 1) return p; if (p in mem.get()) return mem.get()[p]; const result = next(p - 1) + next(p - 2); mem.get()[p] = result; return result; },
-
Embedded (Optional): This optional part allows you to define constants that you want to make accessible as dependencies to compose methods. It's similar to the concept of dependency injection in object-oriented programming. Embedded dependencies are also included in the output generated by Alnico.
Naming Inspiration:
The name Alnico is inspired by an iron alloy that combines three additional elements: aluminum (Al), nickel (Ni), and cobalt (Co). This combination results in a powerful permanent magnet with exceptional resistance to demagnetization.
Continuing from the previous discussion, each state variable in Alnico is a wrapper around three
methods: get, set, and exc. As expected, get() retrieves the current value, set(newValue)
updates the value with a new one, and exc(newValue) performs a combination of reading the old
value and writing the new one.
Alnico offers a secondary utility function called lazily:
import { lazily } from 'alnico';This function is designed to work with state variables. It allows you to initialize or set a state
with a value that's calculated only when needed, specifically during calls to get() and
exc(newValue). The lazily function takes a parameter that's a function receiving a single
argument – the dependencies (similar to those used in method composers).
const { getState, setState } = compose<
{ v1: number; v2: number },
{
calcV2: () => number;
getState: () => { v1: number; v2: number };
setState: (f: number) => void;
},
{ multiply: number; expensiveCalc: (factor: number) => number }
>(
{
v1: 10,
/**
* Since the `calcV2` method (which depends on the `multiply` variable from the embedded
* part) isn't defined until the composition is complete (therefore unknown at the
* beginning), we initialize `v2` lazily.
*/
v2: lazily(({ calcV2 }) => calcV2()),
},
{
/**
* We define the method to reuse it in two places. Note that it depends on the embedded
* part, which is expected to be injected as an option.
*/
calcV2: ({ v1, multiply }) => v1.get() * multiply,
getState: ({ v1, v2 }) => ({ v1: v1.get(), v2: v2.get() }),
setState: ({ v1, v2 }, f) => {
// It's too expensive to calculate if there's a chance the value will never be requested
v1.set(lazily(({ expensiveCalc }) => expensiveCalc(f)));
// If we call `calcV2` right away, it undermines our effort to set `v1` lazily
v2.set(lazily(({ calcV2 }) => calcV2()));
},
},
/**
* The embedded part serves to hold injected dependencies when `compose` is used inside a
* factory function.
*/
{
// `multiply` is assumed to be an injected parameter
multiply: 3,
// This method is injected too
expensiveCalc,
}
);
getState(); // { v1: 10, v2: 30 }
setState(5);
getState(); // { v1: 5, v2: 15 }
setState(8); // Nothing was calculated
setState(10);
getState(); // { v1: 55, v2: 165 }Another scenario where lazily proves useful is within the embedded part:
const { minOf3, minOf5 } = compose<
{ v1: number; v2: number },
{ min: () => number; setVs: (v1: number, v2: number) => void },
{
base: number;
levelUp: (v: number) => number;
minOf3: (v1: number, v2: number, v3: number) => number;
minOf5: (v1: number, v2: number, v3: number, v4: number, v5: number) => number;
}
>(
{
/**
* `lazily` here prevents executing the methods without prior initialization of variables
* `v1` and `v2`.
*/
v1: lazily(() => {
throw new Error('The value must be set');
}),
v2: lazily(() => {
throw new Error('The value must be set');
}),
},
{
min: ({ v1, v2 }) => (v1.get() > v2.get() ? v2.get() : v1.get()),
setVs: ({ v1: { set: setV1 }, v2: { set: setV2 } }, v1, v2) => {
setV1(v1);
setV2(v2);
},
},
{
base: 50,
// `levelUp` depends on methods and `base` which is another embedded variable
levelUp: lazily(({ setVs, min, base }) => (v) => {
setVs(base, v);
return min();
}),
/**
* The result of the following `lazily` execution is 2 more embedded methods that we emit
* using the spreading syntax.
*/
...lazily(({ min, setVs, levelUp }) => ({
minOf3: (v1, v2, v3) => {
setVs(v1, v2);
setVs(min(), v3);
return levelUp(min());
},
/**
* `minOf5` depends on `minOf3`. Both are results of the same lazy execution. We can use
* `lazily` inside it making sure that `minOf3` is already defined at the moment.
*/
minOf5: lazily(
({ minOf3, levelUp }) =>
(v1, v2, v3, v4, v5) =>
levelUp(minOf3(minOf3(v1, v2, v3), v4, v5))
),
})),
}
);
minOf3(20, 5, 15); // 5
minOf3(60, 55, 80); // 50
minOf5(120, 60, 70, 80, 65); // 50
minOf5(120, 80, 75, 54, 33); // 33