28 lines
678 B
Markdown
28 lines
678 B
Markdown
### once
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Ensures a function is called only once.
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Utilizing a closure, use a variable flag and set it to true once the function is called
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for the first time, preventing it from being called again. Allow the function to be supplied
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with an arbitrary number of arguments using the spread/rest (`...`) operator.
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```js
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const once = fn => {
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let called = false;
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return (...args) => {
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if (!called) {
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fn(...args);
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called = true;
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}
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};
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};
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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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