Michael B. White

“function imgLoad(url) { return new Promise(function(resolve, reject) { var request = new XMLHttpRequest(); request.open('GET', url); request.responseType = 'blob'; request.onload = function() { if (request.status === 200) { resolve(request.response); } else { reject(Error('Image didn\'t load successfully; error code:' + request.statusText)); } }; request.onerror = function() { reject(Error('There was a network error.')); }; request.send(); }); }”
― Michael B. White, Mastering JavaScript: A Complete Programming Guide Including jQuery, AJAX, Web Design, Scripting and Mobile Application Development

“var -  used to declare variables with the option of initializing the variable to a value let – used for declaring local values with a block scope and the option of initializing the variable to a value const – used to declare read-only named constants with block scope.”
― Michael B. White, Mastering JavaScript: A Complete Programming Guide Including jQuery, AJAX, Web Design, Scripting and Mobile Application Development