function return a promise javascript code example

Example 1: javascript return promise

function doSomething() {
  return new Promise((resolve, reject) => {
    console.log("It is done.");
    // Succeed half of the time.
    if (Math.random() > .5) {
      resolve("SUCCESS")
    } else {
      reject("FAILURE")
    }
  })
}

const promise = doSomething(); 
promise.then(successCallback, failureCallback);

Example 2: 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 3: what is promise in javascript

Promises make async javascript easier as they are easy to use and write than callbacks. Basically , promise is just an object , that gives us either success of async opertion or failue of async operations

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