85 lines
2.9 KiB
JavaScript
85 lines
2.9 KiB
JavaScript
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"use strict";
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/* global module, require */
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module.exports = function () {
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"use strict";
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// Get a promise object. This may be native, or it may be polyfilled
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var ES6Promise = require("./promise.js");
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/**
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* thatLooksLikeAPromiseToMe()
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*
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* Duck-types a promise.
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*
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* @param {object} o
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* @return {bool} True if this resembles a promise
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*/
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function thatLooksLikeAPromiseToMe(o) {
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return o && typeof o.then === "function" && typeof o.catch === "function";
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}
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/**
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* promisify()
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*
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* Transforms callback-based function -- func(arg1, arg2 .. argN, callback) -- into
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* an ES6-compatible Promise. Promisify provides a default callback of the form (error, result)
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* and rejects when `error` is truthy. You can also supply settings object as the second argument.
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*
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* @param {function} original - The function to promisify
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* @param {object} settings - Settings object
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* @param {object} settings.thisArg - A `this` context to use. If not set, assume `settings` _is_ `thisArg`
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* @param {bool} settings.multiArgs - Should multiple arguments be returned as an array?
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* @return {function} A promisified version of `original`
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*/
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return function promisify(original, settings) {
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return function () {
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for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
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args[_key] = arguments[_key];
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}
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var returnMultipleArguments = settings && settings.multiArgs;
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var target = void 0;
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if (settings && settings.thisArg) {
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target = settings.thisArg;
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} else if (settings) {
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target = settings;
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}
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// Return the promisified function
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return new ES6Promise(function (resolve, reject) {
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// Append the callback bound to the context
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args.push(function callback(err) {
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if (err) {
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return reject(err);
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}
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for (var _len2 = arguments.length, values = Array(_len2 > 1 ? _len2 - 1 : 0), _key2 = 1; _key2 < _len2; _key2++) {
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values[_key2 - 1] = arguments[_key2];
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}
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if (false === !!returnMultipleArguments) {
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return resolve(values[0]);
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}
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resolve(values);
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});
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// Call the function
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var response = original.apply(target, args);
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// If it looks like original already returns a promise,
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// then just resolve with that promise. Hopefully, the callback function we added will just be ignored.
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if (thatLooksLikeAPromiseToMe(response)) {
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resolve(response);
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}
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});
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};
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};
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}();
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