making promises in js

JavaScript
var promise = new Promise(function(resolve, reject) {
  // do some long running async thing…
  
  if (/* everything turned out fine */) {
    resolve("Stuff worked!");
  }
  else {
    reject(Error("It broke"));
  }
});

//usage
promise.then(
  function(result) { /* handle a successful result */ },
  function(error) { /* handle an error */ }
);/*
	A Promise is a proxy for a value not necessarily known when the promise is created. 
    It allows you to associate handlers with an asynchronous action's eventual success 
    value or failure reason.
*/            
let promise = new Promise((resolve , reject) => {
  fetch("https://myAPI")
    .then((res) => {
      // successfully got data
      resolve(res);
    })
    .catch((err) => {
      // an error occured
      reject(err);
    });          
});//Promise to load a file...
//use with openFile(url, fCallback);
//fCallback(fileContents){ //do something with fileContents}
const loadFile = url => {
    return new Promise(function(resolve, reject) {
        //Open a new XHR
        var request = new XMLHttpRequest();
        request.open('GET', url);
        // When the request loads, check whether it was successful
        request.onload = function() {
            if (request.status === 200) {
                // If successful, resolve the promise
                resolve(request.response);
            } else {
                // Otherwise, reject the promise
                reject(Error('An error occurred while loading image. error code:' + request.statusText));
            }
        };
        request.send();
    });
};
const openFile = (url, processor) => {
    loadFile(url).then(function(result) {
            processor(result);
        },
        function(err) {
            console.log(err);
        });
};getData()
    .then(data => console.log(data))
    .catch(error => console.log(error));function getData() {
    return new Promise((resolve, reject)=>{
        request( `http://www.omdbapi.com/?t=The+Matrix`, (error, res, movieData)=>{
            if (error) reject(error);
            else resolve(movieData);
        });
    });
}
Source

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