A snippet to provide utility methods for jQuery's Promise (jQuery.Deferred subset).

jq-promise.js

/**
 * jq-promise.js
 *
 * (c) 2018 koohq. Licensed under CC0.
 * https://creativecommons.org/publicdomain/zero/1.0/legalcode
 */
var $Promise = (function($) {

  function create(func) {
    var deferred = $.Deferred();
    func(deferred.resolve, deferred.reject);
    return deferred.promise();
  }

  function resolve(value) {
    return $.Deferred().resolve(value).promise();
  }

  function reject(reason) {
    return $.Deferred().reject(reason).promise();
  }

  function all($promises) {
    return $.when.apply($, $promises).then(function() {
      return Array.prototype.slice.call(arguments);
    });
  }

  function race($promises) {
    var deferred = $.Deferred();
    $promises.forEach(function($promise) {
      $promise.then(deferred.resolve, deferred.reject);
    });
    return deferred.promise();
  }

  return {
    create: create,
    all: all,
    race: race,
    reject: reject,
    resolve: resolve
  };
})(jQuery);

jq-promise.usage.js

/**
 * jq-promise.usage.js
 *
 * (c) 2017 koohq. Licensed under CC0.
 * https://creativecommons.org/publicdomain/zero/1.0/legalcode
 */

/** $Promise.create **/
// [After] Creates jQuery's Promise by $Promise
var promiseA = $Promise.create(function(resolve, reject) {
   /*
   if (condition) {
     resolve();  
   } else {
     reject();
   }
   */
});

// [Before] Creates jQuery's Promise normally
var promiseB = (function() {
  var deferred = $.Deferred();
  /*
  if (condition) {
    deferred.resolve();  
  } else {
    deferred.reject();
  }
 */
  return deferred.promise();
})();

// Creates Promise(Native). $Promise.create's parameter imitates this.
var promiseN = new Promise(function(resolve, reject) {
  /*
  if (condition) {
    resolve();  
  } else {
    reject();
  }
  */
});


/** $Promise.resolve **/
var $resolved = $Promise.resolve(1);

// Promise.resolve(Native)
var resolved = Promise.resolve(1);


/** $Promise.reject **/
var $rejected = $Promise.reject('An unexpected error occurred');

// Promise.reject(Native)
var rejected = Promise.reject('An unexpected error occurred');


/** $Promise.race **/
var $raced = $Promise.race([$Promise.create(function(resolve, reject) {
  setTimeout(resolve, 10);
}), $rejected]);

// Promise.race(Native)
var raced = Promise.race([new Promise(function(resolve, reject) {
  setTimeout(resolve, 10);
}), rejected]);


/** $Promise.all **/
var $all = $Promise.all([$Promise.create(function(resolve, reject) {
  setTimeout(resolve, 10);
}), $resolved]);

// Promise.all(Native)
var all = Promise.all([new Promise(function(resolve, reject) {
  setTimeout(resolve, 10);
}), resolved]);