Javascript promise chain

javascript_promise_chain_1.js

function callService(param, shouldThrow) {
    return new Promise(function(resolve, reject) {
        setTimeout(function() {
            if (shouldThrow) {
                reject("Hatalı: " + param);
            } else {
                resolve("Başarılı: " + param);
            }
        }, 300);
    });
}

function callServiceA(param) {
    return callService(param, false);
}

function callServiceB(param) {
    return callService(param, false);
}

function callServiceC(param) {
    return callService(param, true);
}

function callServiceD(param) {
    return callService(param, false);
}

function log(label, promise) {
    let begin;
    return (response) => {
        return new Promise(function(resolve) {
            begin = performance.now();
            console.log(`${label} başladı.`);
            resolve(response);
        })
        .then(promise)
        .then(res => {
            console.log(`${label} bitti. Cevap: "${res}". Geçen süre: ${(performance.now() - begin)}.`);
            return res;
        });
    };
}

let promise = log("A servisi", callServiceA)("test")
    .then(log("B servisi", callServiceB))
    .then(log("C servisi", callServiceC))
    .then(log("D servisi", callServiceD))
    .catch(console.log);

let result = await promise;