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45 lines
1016 B
Markdown
45 lines
1016 B
Markdown
# head
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Returns the first element of an array.
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This function takes an array and returns the first element of the array. If the array is empty, the function returns `undefined`.
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## Signature
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```typescript
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export function head<T>(arr: [T, ...T[]]): T;
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export function head<T>(arr: T[]): T | undefined;
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```
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### Parameters
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- `arr` (`T[]`): The array from which to get the first element.
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### Returns
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(`T | undefined`): The first element of the array, or `undefined` if the array is empty.
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## Examples
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```typescript
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const arr1 = [1, 2, 3];
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const firstElement1 = head(arr1);
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// firstElement1 will be 1
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const arr2: string[] = [];
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const firstElement2 = head(arr2);
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// firstElement2 will be undefined
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const arr3 = ['a', 'b', 'c'];
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const firstElement3 = head(arr3);
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// firstElement3 will be 'a'
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const arr4 = [true, false, true];
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const firstElement4 = head(arr4);
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// firstElement4 will be true
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const arr5: [number, string, boolean] = [1, 'a', true];
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const firstElement5 = head(arr5);
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// firstElement5 will be 1
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```
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