88 lines
2.1 KiB
Markdown
88 lines
2.1 KiB
Markdown
# one-time
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Call the supplied function exactly one time. This prevents double callback
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execution. This module can be used on both Node.js, React-Native, or browsers
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using Browserify. No magical ES5/6 methods used unlike the `once` module does
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(except for the async version).
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## Installation
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This module is published to the public npm registry and can be installed
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by running:
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```sh
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npm install --save one-time
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```
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## Usage (normal)
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Simply supply the function with the function that should only be called one
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time:
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```js
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var one = require('one-time');
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function load(file, fn) {
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fn = one(fn);
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eventemitter.once('load', fn);
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eventemitter.once('error', fn);
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// do stuff
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eventemitter.emit('error', new Error('Failed to load, but still finished'));
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eventemitter.emit('load');
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}
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function example(fn) {
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fn = one(fn);
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fn();
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fn('also receives all arguments');
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fn('it returns the same value') === 'bar';
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fn('never');
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fn('gonna');
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fn('give');
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fn('you');
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fn('up');
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}
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example(function () {
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return 'bar'
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});
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```
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## Usage (async)
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The same pattern is available for **async** functions as well, for that you
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should import that `one-time/async` version instead. This one is optimized
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for **async** and **await** support. It following exactly the same as the
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normal version but assumes it's an `async function () {}` that it's wrapping
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instead of a regular function, and it will return an `async function() {}`
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instead of a regular function.
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```js
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import one from 'one-time/async';
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const fn = one(async function () {
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return await example();
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});
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await fn();
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await fn();
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await fn();
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```
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### Why not `once`?
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The main reason is that `once` cannot be used in a browser environment unless
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it's ES5 compatible. For a module as simple as this I find that unacceptable. In
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addition to that it super heavy on the dependency side. So it's totally not
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suitable to be used in client side applications.
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In addition to that we make sure that your code stays easy to debug as returned
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functions are named in the same way as your supplied functions. Making heap
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inspection and stack traces easier to understand.
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## License
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[MIT](LICENSE)
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