Promise Examples

file.js

//Promises take a function that receives callbacks that can be run when an operation completes
let delay5Seconds = new Promise(function(resolve, reject) {
    setTimeout(resolve, 5000);
});


//You can respond to the results of a successfully resolved Promise using the `then` function
delay5Seconds.then(function() {
    console.log('This gets logged 5 seconds later')
});


// Fetch is a browser API that makes HTTP requests and wraps the reply in a Promise
// Promise responses can be chained, and errors can be caught
fetch('/some/data').then(getMessageFromData).then(displayMessage).catch(function() {
    alert('Failed to load data');
});

function getMessageFromData(data) {
    return data.message
}

function displayMessage(message) {
    alert(message);
}