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41 lines
2.0 KiB
41 lines
2.0 KiB
module.exports = {
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// ================================================= Array helpers =================================================
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// Cut an array into an array of sized-length arrays
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// Example: chunk([1,2,3,4,5,6,7,8], 3) → [[1,2,3],[4,5,6],[7,8]]
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chunk: (array, size = 1) =>
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Array.from({ length: Math.ceil(array.length / size) }, (_, i) => array.slice(i * size, i * size + size)),
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// Cartesian cross product of an array of arrays
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// Example: product([1,2],[a,b,c],[true]) → [[1,a,true],[1,b,true],[1,c,true],[2,a,true],[2,b,true],[2,c,true]]
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product: (...arrays) => arrays.reduce((a, b) => a.flatMap(ai => b.map(bi => [...ai, bi])), [[]]),
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// Range from start to end in increment
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// Example: range(17,42,7) → [17,24,31,38]
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range: (start, stop = undefined, step = 1) => {
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if (stop == undefined) {
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stop = start;
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start = 0;
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}
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return start < stop ? Array.from({ length: (stop - start + step - 1) / step }, (_, i) => start + i * step) : [];
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},
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// Unique elements, with an optional getter function
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// Example: unique([1,1,2,3,4,8,1,3,8,13,42]) → [1,2,3,4,8,13,42]
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unique: (array, op = x => x) => array.filter((obj, i) => array.findIndex(entry => op(obj) === op(entry)) === i),
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// Zip arrays together. If some arrays are smaller, undefined is used as a filler.
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// Example: zip([1,2],[a,b,c],[true]) → [[1,a,true],[2,b,undefined],[undefined,c,undefined]]
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zip: (...args) => Array.from({ length: Math.max(...args.map(arg => arg.length)) }, (_, i) => args.map(arg => arg[i])),
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// ================================================ Object helpers =================================================
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// Create a new object by mapping the values through a function, keeping the keys. Second function can be used to pre-filter entries
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// Example: mapValues({a:1,b:2,c:3}, x => x**2) → {a:1,b:4,c:9}
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mapValues: (obj, fn, fn2 = () => true) =>
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Object.fromEntries(
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Object.entries(obj)
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.filter(fn2)
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.map(([k, v]) => [k, fn(v)]),
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),
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};
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