【JavaScript】Promiseの使い方

function doSomething() {
    return new Promise((resolve, reject) => {
        resolve("WWW");
    });
}

function doSomething2() {
    return new Promise((resolve, reject) => {
        reject("XXX");
    });
}

doSomething().then((data) => {
    console.log(data); // WWW
}).catch((data) => {
    console.log(data);
});

doSomething2().then((data) => {
    console.log(data);
}).catch((data) => {
    console.log(data); // XXX
});