JavaScript uses promise objects to implement asynchronous programming _javascript techniques

The Promise object is a unified interface provided by the COMMONJS workgroup for asynchronous programming, which provides native support for promise in ECMASCRIPT6, and promise is what happens in the future, and using promise avoids the layer nesting of callback functions, It also provides the specification for easier control of asynchronous operations. Provides methods such as Reject,resolve,then and catch.

Using Promise

Promise is the native object after ES6, we just need to instantiate the Promise object and use it directly.
Instantiate promise:

var promise = new Promise (function (resolve, reject) {
  console.log (' Begin do something ');
  if (Math.random () * 10.0 > 5) {
    Console.log ("Run Success");
    Resolve ();
  } else {
    Console.log ("Run Failed");
    Reject ();

  }
);

This defines a callback method function (Resolve,reject) that, if successful, calls resolve, and the reject is invoked if it fails.
Promise.prototype.then is a callback after Promise is executed, you can specify resolve and reject callbacks separately using the then method.

Promise.then (function () {
  Console.log (' Resolve from promise ');
}, Function () {
  console.log (' Reject From promise ');

Implementation results One:

Begin do something
 run success
 resolve from Promise

Implementation Result II:

Begin do something
 run failed
 reject from promise

Using Promise for network requests

getrequest = function (URL) {
  var promise = new Promise (function (resolve, reject) {
    var request = require (' Reque St ');
    Request (URL, function (error, respones, body) {
      if (error) {
        reject (error);
        return;
      }
      if (Respones.statuscode = =) {
        Resolve (body)

      } else {
        reject (respones.status);

      }
  }); return
  promise;

};

Getrequest ("https://github.com/"). Then (function (Result) {
  console.log (result);
}, Function (Error) {
  console.error (' Error ', error);
};

Use promise for network requests, or you can use promise to implement AJAX requests on browsing.

Code Address: Https://github.com/jjz/node