broken promise
Trouble with image access in a promise script
by gromiczek
CSS
img {
height:1125px;
width:750px;
}
JavaScript
function imgLoad(url) {
// Create new promise with the Promise() constructor;
// This has as its argument a function
// with two parameters, resolve and reject
return new Promise(function(resolve, reject) {
// Standard XHR to load an image
var request = new XMLHttpRequest();
request.open('GET', url);
request.responseType = 'blob';
// When the request loads, check whether it was successful
request.onload = function() {
if (request.status === 200) {
// If successful, resolve the promise by passing back the request response
resolve(request.response);
} else {
// If it fails, reject the promise with a error message
reject(Error('Image didn\'t load successfully; error code:' + request.statusText));
}
};
request.onerror = function() {
// Also deal with the case when the entire request fails to begin with
// This is probably a network error, so reject the promise with an appropriate message
reject(Error('There was a network error.'));
};
// Send the request
request.send();
});
}
// Get a reference to the body element, and create a new image object
var body = document.querySelector('body');
var myImage = new Image();
// Call the function with the URL we want to load, but then chain the
// promise then() method on to the end of it. This contains two callbacks
imgLoad('https://www.dropbox.com/s/i7ptcure9tlw8pl/Pensive%20Parakeet.jpg?dl=0').then(function(response) {
// The first runs when the promise resolves, with the request.reponse
// specified within the resolve() method.
var imageURL = window.URL.createObjectURL(response);
myImage.src = imageURL;
body.appendChild(myImage);
// The second runs when the promise
// is rejected, and logs the Error specified with the reject() method.
}, function(Error) {
console.log(Error);
});