20 lines
642 B
Markdown
20 lines
642 B
Markdown
### once
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Ensures a function is called only once.
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Utilizing a closure, use a flag, `called`, and set it to `true` once the function is called for the first time, preventing it from being called again.
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Allow the function to be supplied with an arbitrary number of arguments using the spread (`...`) operator.
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```js
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const once = fn =>
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(called => (...args) => (!called ? ((called = true), fn(...args)) : undefined))();
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```
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```js
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const startApp = event => {
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// initializes the app
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console.log(event); // access to any arguments supplied
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};
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document.addEventListener('click', once(startApp)); // only runs `startApp` once upon click
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```
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