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61 lines
2.6 KiB
Markdown
61 lines
2.6 KiB
Markdown
# promisify-simple-callback
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Promisifies a function that expects a callback with a single (result) argument - in other words, a callback that looks like `function(result) { ... }` - in what should be a reasonably performant manner.
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Because sometimes, a module just doesn't conform to the Node.js callback convention.
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## License
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[WTFPL](http://www.wtfpl.net/txt/copying/) or [CC0](https://creativecommons.org/publicdomain/zero/1.0/), whichever you prefer. A donation and/or attribution are appreciated, but not required.
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## Donate
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My income consists largely of donations for my projects. If this module is useful to you, consider [making a donation](http://cryto.net/~joepie91/donate.html)!
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You can donate using Bitcoin, PayPal, Flattr, cash-in-mail, SEPA transfers, and pretty much anything else.
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## Contributing
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Pull requests welcome. Please make sure your modifications are in line with the overall code style, and ensure that you're editing the files in `src/`, not those in `lib/`.
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Build tool of choice is `gulp`; simply run `gulp` while developing, and it will watch for changes.
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Be aware that by making a pull request, you agree to release your modifications under the licenses stated above.
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## Usage
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```javascript
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var Promise = require("bluebird");
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var promisifySimpleCallback = require("promisify-simple-callback");
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/* Pretend that brokenAsyncMethod comes from a third-party library. */
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function brokenAsyncMethod(someArg, options, cb) {
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doSomething(options, function(err, result) {
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cb(result);
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})
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}
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/* Promisify it! */
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var promisifiedAsyncMethod = promisifySimpleCallback(brokenAsyncMethod, [null, {}]);
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/* Now we can use it normally. */
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Promise.try(function() {
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return promisifiedAsyncMethod("foobar");
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}).then(function(result) {
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console.log("Done!", result);
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});
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```
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## API
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### promisifySimpleCallback(func, [defaults])
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Promisifies the given `func`. The promisified method will also catch any synchronous errors, and propagate them as rejections.
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You can also specify default argument values; often, there are optional arguments that come before the callback, and by specifying default values, you can make these arguments *really* optional.
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Because promisification works by appending a callback at the end of the arguments list, you would otherwise have to include all the optional arguments just to make sure the callback ends up in the right place.
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* __func__: The callback-expecting function to promisify.
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* __defaults__: *Optional.* An array of default arguments to fill in. Any argument for which you specify `null` will be skipped - that is, it will be left exactly as is. This means that, for an unspecified argument, it is left to `undefined`.
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