isNotOkay/promise-chain-builder

Promise-Chain-Builder

Utility to generate source code for promise chains

Usage

/*
 Build dynamic promise chain consisting of
 GET-requests at runtime and execute code using 'eval'.
 **/
var request = require('request-promise');
var PCB = require("promise-chain-builder");

var options = {
    resolveWithFullResponse: true
};

// === functions to be chained ===
function getGoogle() {
    options.uri = 'http://www.google.de';
    return request(options);
}

function getWikipedia(res) {
    console.log('// status code of previous GET-request: ' + res.statusCode);
    options.uri = 'http://www.wikipedia.org';
    return request(options);
}

function getReddit(res) {
    console.log('// status code of previous GET-request: ' + res.statusCode);
    options.uri = 'http://www.reddit.org';
    return request(options);
}

function somethingWentWrong(err) {
    console.log(err);
}

function finish(res) {
    console.log('// status code of previous GET-request: ' + res.statusCode);
}
// === functions to be chained ===

// build chain
var pcb = new PCB([getGoogle, getWikipedia, getReddit, finish]);
pcb.setCatch(somethingWentWrong);
var source = pcb.source();
console.log(source);

// execute chain
eval(source);

Output

getGoogle().then(function getWikipedia(res) {
    console.log('// status code of previous GET-request: ' + res.statusCode);
    options.uri = 'http://www.wikipedia.org';
    return request(options);
}).then(function getReddit(res) {
    console.log('// status code of previous GET-request: ' + res.statusCode);
    options.uri = 'http://www.reddit.org';
    return request(options);
}).then(function finish(res) {
    console.log('// status code of previous GET-request: ' + res.statusCode);
}).catch(function somethingWentWrong(err) {
    console.log(err);
});
// status code of previous GET-request: 200
// status code of previous GET-request: 200
// status code of previous GET-request: 200

API

push(func)

Appends a function wrapped in a 'then'-block.

size()

Returns number of chained functions.

source([fileName])

Returns generated source code. If fileName is set, source will be written to file.

setCatch(func);

Appends a 'catch'-function at the end of the chain to handle errors.