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promiseXHR.js
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promiseXHR.js
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/**
* A Promise based XHR function to get JSON data from external APIs
*
* Browser compatibility: Chrome, Edge, Firefox, Opera, Safari.
* Internet Explorer does not support the Promise object natively.
*
*
* @param {String} url - The request URL
* @param {Object} options - A set of options for the request
* @return {Promise} - The XHR request Promise
*/
function getJSON (url, options) {
// Create the XHR request
var request = new XMLHttpRequest();
// Setup the Promise
var xhrPromise = new Promise( (resolve, reject) => {
// Setup our listener to process compeleted requests
request.onreadystatechange = () => {
// Only run if the request is complete
if (request.readyState !== 4) return;
// Process the response
if (request.status >= 200 && request.status < 300) {
// If successful, resolve the promise by passing back the request response
resolve(request.response);
} else {
// If it fails, reject the promise
reject({
status: request.status,
statusText: request.statusText
});
}
};
request.onerror = () => {
reject(Error('There was a network error.'));
};
// Convert the API params object to a serialized query string
var query = options.apiquery;
if(query !== null) {
var query = "?" + Object
.keys(query)
.map(function(key){
return key+"="+encodeURIComponent(query[key]);
})
.join("&");
}
// Setup our HTTP request
if(!options.method) options.method = 'GET';
request.open(options.method, url + query, true); // method, url, async
request.responseType = 'json';
request.setRequestHeader('Accept', 'application/json');
// Send the request
request.send();
});
// Return the request as a Promise
return xhrPromise;
} // getJSON