66 lines
1.4 KiB
Markdown
66 lines
1.4 KiB
Markdown
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# @gar/promisify
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### Promisify an entire object or class instance
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This module leverages es6 Proxy and Reflect to promisify every function in an
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object or class instance.
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It assumes the callback that the function is expecting is the last
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parameter, and that it is an error-first callback with only one value,
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i.e. `(err, value) => ...`. This mirrors node's `util.promisify` method.
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In order that you can use it as a one-stop-shop for all your promisify
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needs, you can also pass it a function. That function will be
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promisified as normal using node's built-in `util.promisify` method.
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[node's custom promisified
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functions](https://nodejs.org/api/util.html#util_custom_promisified_functions)
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will also be mirrored, further allowing this to be a drop-in replacement
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for the built-in `util.promisify`.
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### Examples
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Promisify an entire object
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```javascript
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const promisify = require('@gar/promisify')
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class Foo {
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constructor (attr) {
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this.attr = attr
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}
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double (input, cb) {
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cb(null, input * 2)
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}
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const foo = new Foo('baz')
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const promisified = promisify(foo)
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console.log(promisified.attr)
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console.log(await promisified.double(1024))
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```
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Promisify a function
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```javascript
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const promisify = require('@gar/promisify')
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function foo (a, cb) {
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if (a !== 'bad') {
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return cb(null, 'ok')
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}
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return cb('not ok')
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}
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const promisified = promisify(foo)
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// This will resolve to 'ok'
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promisified('good')
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// this will reject
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promisified('bad')
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```
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