Relaunching mobile.de
with Node.js and ES6

29th eBay Tech Talk in Berlin, Germany

Patrick Hund, software developer at mobile.de

  • 9 weeks
  • 7 engineers
  • 10.81M visitors / month*
  • ~300 requests / second

* AGOF Digital Facts 2015-06

Why?

Universal JavaScript

Lessons Learned

Bad Example – do not do this!

config.js


export default {
    serviceUrl: "http://my.service/endpoint",
    timeout: 1000
}

service.js


import config from "config";
import axios from "axios";
import withTimeout from "withTimeout";

export default () =>
    withTimeout(axios.get(config.serviceUrl), config.timeout);

service-test.js (excerpt)


describe("When I call the service", () => {
    describe("and the service returns data in time", () => {
        before(setup);
        describe("the resulting promise", () => {
            it("is resolved", () => ok.called.should.be.ok);
            it("is not rejected", () => ko.called.should.not.be.ok);
        });
        after(teardown);
    });
    describe("and the service times out", () => {
        before(setupTimeout);
        describe("the resulting promise", () => {
            it("is rejected", () => ko.called.should.be.ok);
            it("is not resolved", () => ok.called.should.not.be.ok);
        });
        after(teardown);
    });
});

service-test.js (excerpt)


function setupTimeout(done) {
    sinon.stub(axios, "get").returns(new Promise(resolve =>
        setTimeout(() => {
            resolve({
                data: "SOME_DATA"
            });
        }, 2000)
    ));
    ok = sinon.spy();
    ko = sinon.spy();
    result = service().then(() => {
        ok();
        done();
    }).catch(() => {
        ko();
        done();
    });
}

Good Example

config.js


export default {
    get() {
        return {
            serviceUrl: "http://my.service/endpoint",
            timeout: 1000
        };
    }
};

service.js


import configurator from "./config";
import axios from "axios";
import withTimeout from "./withTimeout";

export default () => {
    const config = configurator.get();
    return withTimeout(axios.get(config.serviceUrl), config.timeout);
};

service-test.js (excerpt)


function setupTimeout(done) {
    sinon.stub(axios, "get").returns(new Promise(resolve => setTimeout(() => {
        resolve({
            data: "SOME_DATA"
        });
    }, 10)));
    sinon.stub(config, "get").returns({
        serviceUrl: "http://my.service/endpoint",
        timeout: 0
    });
    ok = sinon.spy();
    ko = sinon.spy();
    result = service().then(() => {
        ok();
        done();
    }).catch(() => {
        ko();
        done();
    });
}
                        

/**
 * withArgs.js
 *
 * Curries a function with additional arguments, which are prepended
 * to the arguments passed to the function.
 *
 * Example:
 *
 * function foo(a, b, c, d) {
 *     console.log(a + b + c + d);
 * }
 *
 * let bar = withArgs(1, 2)(foo);
 *
 * bar(3, 4); // => 10
 *
 * [ 3, 4 ].forEach(bar); // => 6; => 7
 *
 */

export default (...args1) => func => (...args2) => func(...args1, ...args2);

Join our team!

j.rfer.us/EBRhYLmtO

Patrick Hund
Software developer at mobile.de

Follow me on Twitter: @wiekatz

Slides available on GitHub: pahund.github.io/ebaytechtalk29

Visit the eBay Technology blog: technology.ebay.de

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