mixinable
mixinable
is a small functional utility library allowing you to use mixins in your code. More specifically, it allows you to create mixin containers that apply mixin method application strategies to mixin method implementations.
Mixins are plain Objects (or hashes) that can easily be shared, modified and extended using standard language features such as spread syntax or Object.assign()
.
mixinable
allows you to provide custom constructor
functions and supports asynchronous methods returning Promises
. It is built in a functional way, allowing you to, for example, apply fn.bind()
.
Installation
Using NPM:
npm install -S mixinable
Using Yarn:
yarn add mixinable
To be able to use mixinable
, you will have to make sure your environment supports Promise
: if, for example, you need to support IE11, you will have to polyfill Promise
.
API
define(definition)
The main export of mixinable
is a define()
function accepting a mixin container definition. This definition hash is made up of strategy
functions prescribing how to handle different mixin methods you provide.
It returns a variadic mixin()
function that accepts the mixin definitions you want to apply and returns a create()
function. Mixin definitions are hashes containing mixin method implementations that are being applied using the aforementioned strategies.
And that create()
function accepts whatever arguments your constructor()
s accept.
Example
import define from 'mixinable';
const mixin = define({
bar(functions, arg) {
return functions.pop()(arg);
},
});
const create = mixin({
bar(arg) {
console.log(arg);
},
});
const foo = create();
foo.bar('yeah!');
Speaking of which: mixinable
creates a separate hidden mixin instance for every mixin you provide. When used inside a mixin method, this
refers to this hidden instance.
Mixin methods not included in your definition are only accessible from within the mixin instance itself, but not from the outside.
Example
import define from 'mixinable';
const mixin = define({
bar(functions, arg) {
return functions.pop()(arg);
},
});
const create = mixin({
bar(arg) {
this.qux(arg);
},
qux(arg) {
console.log(arg);
},
});
const foo = create();
foo.bar('yeah!');
console.log(typeof foo.bar, typeof foo.qux);
Mixin definitions can be (or contain) custom constructors. These functions are being passed the create()
function's arguments upon creation.
Example
import define from 'mixinable';
const mixin = define();
const create = mixin(
{
constructor: function(arg) {
console.log(arg);
},
},
class {
constructor(arg) {
console.log(arg);
}
}
);
create('yee-hah!');
define.override
override
is a helper implementating a mixin strategy that resembles classical inherintance (class ... extends
): it simply calls the last method implementation.
Example
import define, { override } from 'mixinable';
const mixin = define({
bar: override,
});
const create = mixin(
{
bar() {
console.log(1);
},
},
class {
bar() {
console.log(2);
}
}
);
const foo = create();
foo.bar();
override
returns a Promise
if one of its implementations does. If you want it to always return a Promise
, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.override
.
define.parallel
parallel
is a helper implementating a mixin strategy that executes all defined implementations in parallel. This is probably most useful if asynchronous implementations are involved.
Example
import define, { parallel } from 'mixinable';
const mixin = define({
bar: parallel,
});
const create = mixin(
{
bar(val, inc) {
return Promise.resolve(val + inc);
},
},
class {
bar(val, inc) {
return val + inc;
}
}
);
const foo = create();
foo.bar(0, 1).then(res => console.log(res));
parallel
returns a Promise
if one of its implementations does. If you want it to always return a Promise
, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.parallel
.
define.pipe
pipe
is a helper implementating a strategy that passes each implementation's output to the next, using the first argument as the initial value. All other arguments are being passed to all implementations as-is.
Example
import define, { pipe } from 'mixinable';
const mixin = define({
bar: pipe,
});
const create = mixin(
{
bar(val, inc) {
return Promise.resolve(val + inc);
},
},
class {
bar(val, inc) {
return val + inc;
}
}
);
const foo = create();
foo.bar(0, 1).then(res => console.log(res));
pipe
returns a Promise
if one of its implementations does. If you want it to always return a Promise
, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.pipe
.
define.compose
compose
works essentially identically as pipe
, but in reverse order: the very last implementation receives the initial value and the first implementation returns the final output.
Example
import define, { compose } from 'mixinable';
const mixin = define({
bar: compose,
});
compose
returns a Promise
if one of its implementations does. If you want it to always return a Promise
, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.compose
.
Custom Strategies
You can supply your own mixin strategies: such strategies are plain functions that receive the defined implementations as their first argument. The following example shows a naïve re-implementation of the override
strategy.
Example
import define from 'mixinable';
const mixin = define({
bar(functions, ...args) {
functions.pop().apply(null, args);
},
});
const create = mixin({
bar(arg) {
console.log(arg);
},
});
const foo = create();
foo.bar(1);
Utilities
define.async
All of the strategies described above return a Promise
if one of their implementations does. If you want them to always return a Promise
please use define.async.{override,parallel,pipe,compose}
.
define.sync
If you want to make sure one of the strategies never returns a Promise
please use define.sync.{override,parallel/sequence,pipe,compose}
. If you do, an Error
will be thrown if a Promise
is returned.
define.isMixinable(object)
If you need to check whether an object actually is an instance of a mixinable
, you can simply test it using this function that returns true
or false
.
Contributing
If you want to contribute to this project, create a fork of its repository using the GitHub UI. Check out your new fork to your computer:
mkdir mixinable && cd $_
git clone git@github.com:user/mixinable.git
Afterwards, you can yarn install
the required dev dependencies and start hacking away. When you are finished, please do go ahead and create a pull request.
mixinable
itself is (almost) entirely written in ECMAScript 5 and adheres to semistandard code style. Please make sure your contribution does, too.