instyle

instyle.js

/**
 * @flow
 */

opaque type Ruleset = { [string]: string | number };

type CreateInput = {
  [styleName: string]: CSSProperties
};

type ToRuleset = () => Ruleset;

function create<T: CreateInput>(input: T): $ObjMap<T, ToRuleset> {
  return input;
}

type InStyle = {
  (...styles: Array<CSSProperties | Ruleset>): CSSProperties,
  create: typeof create
};

function _instyle(...styles: Array<CSSProperties | Ruleset>): CSSProperties {
  if (styles.length === 1) {
    return styles[0];
  }
  const result: CSSProperties = styles.reduce((acc, cur) => {
    if (cur != null) {
      for (const key in cur) {
        if (cur.hasOwnProperty(key)) {
          acc[key] = cur[key];
        }
      }
    }
    return acc;
  }, ({}: CSSProperties));
  return result;
}

_instyle.create = create;

const instyle: InStyle = _instyle;

export default instyle;