42 lines
1.8 KiB
JavaScript
42 lines
1.8 KiB
JavaScript
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//#region src/function/rest.ts
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/**
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* Creates a function that transforms the arguments of the provided function `func`.
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* The transformed arguments are passed to `func` such that the arguments starting from a specified index
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* are grouped into an array, while the previous arguments are passed as individual elements.
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*
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* @template F - The type of the function being transformed.
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* @param {F} func - The function whose arguments are to be transformed.
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* @param {number} [startIndex=func.length - 1] - The index from which to start grouping the remaining arguments into an array.
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* Defaults to `func.length - 1`, grouping all arguments after the last parameter.
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* @returns {(...args: any[]) => ReturnType<F>} A new function that, when called, returns the result of calling `func` with the transformed arguments.
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*
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* The transformed arguments are:
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* - The first `start` arguments as individual elements.
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* - The remaining arguments from index `start` onward grouped into an array.
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* @example
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* function fn(a, b, c) {
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* return [a, b, c];
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* }
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*
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* // Using default start index (func.length - 1, which is 2 in this case)
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* const transformedFn = rest(fn);
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* console.log(transformedFn(1, 2, 3, 4)); // [1, 2, [3, 4]]
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*
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* // Using start index 1
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* const transformedFnWithStart = rest(fn, 1);
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* console.log(transformedFnWithStart(1, 2, 3, 4)); // [1, [2, 3, 4]]
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*
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* // With fewer arguments than the start index
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* console.log(transformedFn(1)); // [1, undefined, []]
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*/
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function rest(func, startIndex = func.length - 1) {
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return function(...args) {
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const rest = args.slice(startIndex);
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const params = args.slice(0, startIndex);
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while (params.length < startIndex) params.push(void 0);
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return func.apply(this, [...params, rest]);
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};
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}
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//#endregion
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exports.rest = rest;
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