[Design Pattern: Serial Actions] #JavaScript #Promise

promiseSerial.js

/**
 * Sequentially execute an array of functions that return promises.
 * @example:
 * .then((data)=>{
 *      const functions = data.map( (body) => {
 *                         return () => {
 *                             return requestPromise({
 *                                 method: 'PATCH',
 *                                 uri: `${HOST}:${PORT}/update`,
 *                                 headers: {Authorization: `JWT ${token}`},
 *                                 json: body,
 *                             })
 *                         }
 *                     } );
 *      return promiseSerial(functions);
 * })
 * @param {function[]} functions - An array of functions tha return promises.
 */
const promiseSerial = ( functions ) => {
    return functions.reduce((promise, func) => {
        return promise.then(result => func().then(Array.prototype.concat.bind(result)))
    }, Promise.resolve([]));
};