35 lines
1.2 KiB
TypeScript
35 lines
1.2 KiB
TypeScript
/**
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* Returns the first element of an array.
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*
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* This function takes an array and returns the first element of the array.
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* If the array is empty, the function returns `undefined`.
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*
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* @template T - The type of elements in the array.
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* @param {[T, ...T[]]} arr - A non-empty array from which to get the first element.
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* @returns {T} The first element of the array.
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*
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* @example
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* const arr = [1, 2, 3];
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* const firstElement = head(arr);
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* // firstElement will be 1
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*/
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declare function head<T>(arr: readonly [T, ...T[]]): T;
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/**
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* Returns the first element of an array or `undefined` if the array is empty.
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*
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* This function takes an array and returns the first element of the array.
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* If the array is empty, the function returns `undefined`.
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*
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* @template T - The type of elements in the array.
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* @param {T[]} arr - The array from which to get the first element.
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* @returns {T | undefined} The first element of the array, or `undefined` if the array is empty.
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*
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* @example
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* const emptyArr: number[] = [];
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* const noElement = head(emptyArr);
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* // noElement will be undefined
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*/
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declare function head<T>(arr: readonly T[]): T | undefined;
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export { head };
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