React-compose allows you to encapsulate component logic into smaller, reusable functions, which in turn can be combined back into component. The fundamental idea is that React components has a way of becoming bloated with, often repeated, logic. This lib provides you with a set of tools to avoid that.

The encapsulated pieces will be easily testable, either because they are constant or since their functionality has a more narrow scope than a corresponding component would have.

The other aspect of react-compose is based upon the fact that whenever you create a React component, you also create an api for it as well. It is essential, for any large scale project that this api is well formed and consistent across the application. Most components should also be extendable too, which is why, significant care is needed to make sure that each component doesn't break these rules.

Let's show a simple example of extendablity:

const ButtonComponent = props => {
  const {
    onClick,
    label,
  } = props;
  return <button onClick={onClick}>{label}</button>;
};

Now if a developer would like to manipulate the style of ButtonComponent from the outside, it would have to be changed accordingly:

const ButtonComponent = props => {
  const {
    onClick,
    style,
    label,
  } = props;
  return <button onClick={onClick} style={style}>{label}</button>;
};

On the other hand, if all props should be passed down to the button element, the following is much more useful:

const ButtonComponent = props => {
  const {
    label,
  } = props;
  return <button {...props}>{label}</button>;
};

With react-compose, the above would be written as:

const labelToChildren = ({ label }) => ({ children: label });

const ButtonComponent = compose(labelToChildren)('button');

Leaving much less room for breaking the rules of extendability and resuability. The CustomComponent should essentially work as you would expect that the basic html elements does, ButtonComponent ~ button, beyond of course the added behavior.

As an extra bonus, it is also more straight forward to test the encapsulated behavior rather than the component as a whole.

describe('labelToChildren', () => {
  it('should pass whatever input label as children', () => {
    expect(labelToChildren({ label: 'string' }).children).toEqual('string');
  });
});

Finally, the heart of react-compose, is finding those elementary patterns that are present in your application. In this case, we can create a nice higher order function for the labelToChildren logic.

const mixProp = (from, to) => props => ({ [to]: props[from] });
const labelToChildren = mixProp('label', 'children');

Installation

Install package, and check that you are using a matching version of React (^0.14)

npm install -s react-compose

API

Example api usage:

import { compose } from 'react-compose';

const constantProper = {
  age: 15,
};

const dynamicProper = props => {
  return {
    children: `The cat is ${props.age} years old`,
  };
};

const Cat = compose(constantProper, dynamicProper)('p');

// => <p>The cat is 15 years old</p>;

Specialized style composing

import { compose, styles } from 'react-compose';

const constantStyle = {
  background: 'red',
};
const dynamicStyle = ({ isActive }) => (!isActive && {
  display: 'none',
});

const Component = compose(styles(constantStyle, dynamicStyle))('p');

return (props) => {
  return <Component isActive={false}>Some text</Component>;
};

Stacking custom components

import { compose } from 'react-compose';

const Cat = props => {
  return <p>The cat is {props.age} years old</p>;
};

const injectAge = {
  age: 5,
};

const Composed = compose(injectAge)(Cat);

// => <p>The cat is 5 years old</p>

Composing complex children values

import { compose, children } from 'react-compose';

const AgeInfo = props => {
  return <p>Age: {props.age} years</p>;
};

const LengthInfo = props => {
  return <p>Length: {props.length} cm</p>;
};

const HeightInfo = props => {
  return <p>Height: {props.height} cm</p>;
};

const Info = compose(children(AgeInfo, LengthInfo, HeightInfo))('div');

const dogData = {
  age: 5,
  length: 250,
  height: 150,
};

const DogInfo = compose(dogData)(Info);

// => <div>
//      <p>Age: 5</p>
//      <p>Length: 250</p>
//      <p>Height: 150</p>
//    </div>

Composing classNames, using the awesome classnames lib

import { compose, classNames } from 'react-compose';

const btnClassNames = classNames('btn',
  ({ pressed }) => pressed && 'btn-pressed',
  ({ hover }) => hover && 'btn-hover');
 
const Button = compose(btnClassNames)('button');

// pressed: true => <button className="btn btn-pressed" />
// pressed: false, hover: true => <button className="btn btn-hover" />