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120 lines
2.5 KiB
120 lines
2.5 KiB
2 years ago
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# pify [](https://travis-ci.org/sindresorhus/pify)
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> Promisify a callback-style function
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## Install
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```
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$ npm install --save pify
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```
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## Usage
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```js
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const fs = require('fs');
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const pify = require('pify');
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// promisify a single function
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pify(fs.readFile)('package.json', 'utf8').then(data => {
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console.log(JSON.parse(data).name);
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//=> 'pify'
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});
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// or promisify all methods in a module
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pify(fs).readFile('package.json', 'utf8').then(data => {
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console.log(JSON.parse(data).name);
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//=> 'pify'
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});
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```
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## API
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### pify(input, [promiseModule], [options])
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Returns a promise wrapped version of the supplied function or module.
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#### input
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Type: `function`, `object`
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Callback-style function or module whose methods you want to promisify.
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#### promiseModule
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Type: `function`
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Custom promise module to use instead of the native one.
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Check out [`pinkie-promise`](https://github.com/floatdrop/pinkie-promise) if you need a tiny promise polyfill.
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#### options
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##### multiArgs
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Type: `boolean`
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Default: `false`
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By default, the promisified function will only return the second argument from the callback, which works fine for most APIs. This option can be useful for modules like `request` that return multiple arguments. Turning this on will make it return an array of all arguments from the callback, excluding the error argument, instead of just the second argument.
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```js
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const request = require('request');
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const pify = require('pify');
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pify(request, {multiArgs: true})('https://sindresorhus.com').then(result => {
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const [httpResponse, body] = result;
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});
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```
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##### include
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Type: `array` of (`string`|`regex`)
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Methods in a module to promisify. Remaining methods will be left untouched.
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##### exclude
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Type: `array` of (`string`|`regex`)
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Default: `[/.+Sync$/]`
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Methods in a module **not** to promisify. Methods with names ending with `'Sync'` are excluded by default.
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##### excludeMain
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Type: `boolean`
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Default: `false`
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By default, if given module is a function itself, this function will be promisified. Turn this option on if you want to promisify only methods of the module.
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```js
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const pify = require('pify');
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function fn() {
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return true;
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}
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fn.method = (data, callback) => {
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setImmediate(() => {
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callback(data, null);
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});
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};
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// promisify methods but not fn()
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const promiseFn = pify(fn, {excludeMain: true});
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if (promiseFn()) {
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promiseFn.method('hi').then(data => {
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console.log(data);
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});
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}
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```
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## License
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MIT © [Sindre Sorhus](http://sindresorhus.com)
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