lazy-promise/lib/index.js

A bare-bones lazily-evaluated Promises/A+ implementation.

"use strict";

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

Object.defineProperty(exports, "__esModule", { value: true });
var asap = require('asap');

var LazyPromise = function () {
    function LazyPromise(executor) {
        _classCallCheck(this, LazyPromise);

        this._executor = executor;
    }
    /**
     * Attaches callbacks for the resolution and/or rejection of the Promise.
     * @param onfulfilled The callback to execute when the Promise is resolved.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of which ever callback is executed.
     */


    _createClass(LazyPromise, [{
        key: "then",
        value: function then(onfulfilled, onrejected) {
            var _this = this;

            if (!this._result) {
                this._result = new Promise(function (resolve, reject) {
                    asap(function () {
                        try {
                            _this._executor(resolve, reject);
                        } catch (ex) {
                            reject(ex);
                        }
                    });
                });
            }
            return this._result.then(onfulfilled, onrejected);
        }
        /**
         * Attaches a callback for only the rejection of the Promise.
         * @param onrejected The callback to execute when the Promise is rejected.
         * @returns A Promise for the completion of the callback.
         */

    }, {
        key: "catch",
        value: function _catch(onrejected) {
            return this.then(undefined, onrejected);
        }
    }]);

    return LazyPromise;
}();

exports.default = LazyPromise;
if (Object.setPrototypeOf) {
    Object.setPrototypeOf(LazyPromise.prototype, Promise.prototype);
    Object.setPrototypeOf(LazyPromise, Promise);
} else {
    LazyPromise.prototype.__proto__ = Promise.prototype;
    LazyPromise.__proto__ = Promise;
}
module.exports = LazyPromise;
module.exports.default = LazyPromise;
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