51Degrees Pipeline Node.js  4.4

51Degrees Pipeline for Node.js


This example demonstrates the creation of a custom flow element which takes a birth date as evidence and uses it to check a lookup table for a starsign.This lookup table is stored in a JSON file which is registered using the datafile update service. In this case the file has a simple watcher which checks if the file has changed.

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const path = require('path');
// Require the filesystem module for datafile reading
const fs = require('fs');
// First require the core Pipeline
const FiftyOnePipelineCore = require(path.resolve(__dirname, '../../fiftyone.pipeline.core'));
// Next require the engines extension that extends flowElements to support
// functionality such as auto updating datafiles,
// caches and missing property services
// Note that this example is designed to be run from within the
// source repository. If this code has been copied to run standalone
// then you'll need to replace the require below with the commented
// out version below it.
const FiftyOnePipelineEngines = require(path.resolve(__dirname, '..'));
// const FiftyOnePipelineEngines = require("fiftyone.pipeline.engines");
// Astrology flowElement
class Astrology extends FiftyOnePipelineEngines.Engine {
constructor ({ datafile }) {
// Create a datafile including a filesystem watcher that checks if
// the datafile has changed. Test by changing the names of the
// starsigns to see it update
this.dataFile = new FiftyOnePipelineEngines
flowElement: this,
path: datafile,
autoUpdate: false,
fileSystemWatcher: true
// datakey used to categorise data coming back from
// this flowElement in a pipeline
this.dataKey = 'astrology';
// A filter (in this case a basic list) stating which evidence the
// flowElement is interested in, in this case a query string
this.evidenceKeyFilter = new FiftyOnePipelineCore
// Update the datafile
// A function called when the datafile is updated / refreshed. In this
// case it simply loads the JSON from the file into the engine's memory.
refresh () {
const engine = this;
fs.readFile(this.dataFile.path, 'utf8', function (err, data) {
if (err) {
return console.error(err);
data = JSON.parse(data);
// Load the datafile into memory and parse it to make it
// more easily readable
data = data.map(function (e) {
const start = e[1].split('/');
const end = e[2].split('/');
return {
starsign: e[0],
startMonth: parseInt(start[1]),
startDate: parseInt(start[0]),
endMonth: parseInt(end[1]),
endDate: parseInt(end[0])
engine.data = data;
// Internal processing function
processInternal (flowData) {
let dateOfBirth = flowData.evidence.get('query.dateOfBirth');
// Collect data to save back into the flowData under this engine
const result = {};
// Lookup the date of birth using the provided and now parsed datafile
if (dateOfBirth) {
dateOfBirth = dateOfBirth.split('-');
const month = parseInt(dateOfBirth[1]);
const day = parseInt(dateOfBirth[2]);
result.starSign = this.data.filter(function (date) {
// Find starsigns in the correct month
if (date.startMonth === month) {
if (date.startDate > day) {
return false;
} else if (date.endMonth === month && date.endDate <= day) {
return false;
} else {
return true;
} else if (date.endMonth === month) {
if (date.endDate < day) {
return false;
} else {
return true;
} else {
return false;
// Save the data into an extension of the elementData class
// (in this case a simple dictionary subclass)
const data = new FiftyOnePipelineCore.ElementDataDictionary({
flowElement: this, contents: result
// Set this data on the flowElement
const astrologyElement = new Astrology(
{ datafile: (process.env.directory || __dirname) + '/astrology.json' }
const http = require('http');
const pipeline = new FiftyOnePipelineCore.PipelineBuilder()
const server = http.createServer((req, res) => {
if (req.url !== '/favicon.ico') {
const flowData = pipeline.createFlowData();
// Add any information from the request
// (headers, cookies and additional client side provided information)
flowData.process().then(function () {
// Output the date of birth form with any results if they exist
const output = `
? '<p>Your starsign is ' +
flowData.astrology.starSign + ' </p>'
: '<p>Add your date of birth to get your starsign</p>'
<label for='dateOfBirth'>Date of birth</label>
<input type='date' name='dateOfBirth' id='dateOfBirth'>
<input type='submit'>
res.statusCode = 200;
res.setHeader('Content-Type', 'text/html');
const portNum = process.env.PORT || 3000;
console.info('To test this example, browse to http://localhost:' + portNum);