promises syntax code example

Example 1: javascript promise

var promise = new Promise(function(resolve, reject) {
  // do some long running async thingâ€¦
  
  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 */ }
);

Example 2: js return a promise

function myAsyncFunction(url) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest();
    xhr.open("GET", url);
    xhr.onload = () => resolve(xhr.responseText);
    xhr.onerror = () => reject(xhr.statusText);
    xhr.send();
  });
}

Example 3: promise js

A promise is an object that may produce a single value some time in the future: 
either a resolved value, or a reason that it’s not resolved

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Javascript Example

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