1 | ;
|
2 |
|
3 | Object.defineProperty(exports, "__esModule", {
|
4 | value: true
|
5 | });
|
6 | exports.default = ensureAsync;
|
7 |
|
8 | var _setImmediate = require('./internal/setImmediate');
|
9 |
|
10 | var _setImmediate2 = _interopRequireDefault(_setImmediate);
|
11 |
|
12 | var _initialParams = require('./internal/initialParams');
|
13 |
|
14 | var _initialParams2 = _interopRequireDefault(_initialParams);
|
15 |
|
16 | var _wrapAsync = require('./internal/wrapAsync');
|
17 |
|
18 | function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
|
19 |
|
20 | /**
|
21 | * Wrap an async function and ensure it calls its callback on a later tick of
|
22 | * the event loop. If the function already calls its callback on a next tick,
|
23 | * no extra deferral is added. This is useful for preventing stack overflows
|
24 | * (`RangeError: Maximum call stack size exceeded`) and generally keeping
|
25 | * [Zalgo](http://blog.izs.me/post/59142742143/designing-apis-for-asynchrony)
|
26 | * contained. ES2017 `async` functions are returned as-is -- they are immune
|
27 | * to Zalgo's corrupting influences, as they always resolve on a later tick.
|
28 | *
|
29 | * @name ensureAsync
|
30 | * @static
|
31 | * @memberOf module:Utils
|
32 | * @method
|
33 | * @category Util
|
34 | * @param {AsyncFunction} fn - an async function, one that expects a node-style
|
35 | * callback as its last argument.
|
36 | * @returns {AsyncFunction} Returns a wrapped function with the exact same call
|
37 | * signature as the function passed in.
|
38 | * @example
|
39 | *
|
40 | * function sometimesAsync(arg, callback) {
|
41 | * if (cache[arg]) {
|
42 | * return callback(null, cache[arg]); // this would be synchronous!!
|
43 | * } else {
|
44 | * doSomeIO(arg, callback); // this IO would be asynchronous
|
45 | * }
|
46 | * }
|
47 | *
|
48 | * // this has a risk of stack overflows if many results are cached in a row
|
49 | * async.mapSeries(args, sometimesAsync, done);
|
50 | *
|
51 | * // this will defer sometimesAsync's callback if necessary,
|
52 | * // preventing stack overflows
|
53 | * async.mapSeries(args, async.ensureAsync(sometimesAsync), done);
|
54 | */
|
55 | function ensureAsync(fn) {
|
56 | if ((0, _wrapAsync.isAsync)(fn)) return fn;
|
57 | return (0, _initialParams2.default)(function (args, callback) {
|
58 | var sync = true;
|
59 | args.push(function () {
|
60 | var innerArgs = arguments;
|
61 | if (sync) {
|
62 | (0, _setImmediate2.default)(function () {
|
63 | callback.apply(null, innerArgs);
|
64 | });
|
65 | } else {
|
66 | callback.apply(null, innerArgs);
|
67 | }
|
68 | });
|
69 | fn.apply(this, args);
|
70 | sync = false;
|
71 | });
|
72 | }
|
73 | module.exports = exports['default']; |
\ | No newline at end of file |