Waiting on multiple async operations using Promises

file.js

//fetch makes an HTTP request and returns a promise that resolves 
//when the file is loaded
let p1 = fetch('/data/file1.json');
let p2 = fetch('/data/file2.json');
let p3 = fetch('/data/file3.json');

Promise.all([p1,p2,p3]).then(function(values) {
    //values contains the responses from each of the promises
    let [response1, response2, response3] = values;

    doStuffWithResponses(response1, response2, response3);
}).catch(function() {
    alert('failed to load one of the files')
});