JavaScript Promises Asynchronous API request
Example
This is an example of a simple GET API call wrapped in a promise to take advantage of its asynchronous functionality.
var get = function(path) {
return new Promise(function(resolve, reject) {
let request = new XMLHttpRequest();
request.open('GET', path);
request.onload = resolve;
request.onerror = reject;
request.send();
});
};
More robust error handling can be done using the following onload and onerror functions.
request.onload = function() {
if (this.status >= 200 && this.status < 300) {
if(request.response) {
// Assuming a successful call returns JSON
resolve(JSON.parse(request.response));
} else {
resolve();
} else {
reject({
'status': this.status,
'message': request.statusText
});
}
};
request.onerror = function() {
reject({
'status': this.status,
'message': request.statusText
});
};
