39 lines
1.1 KiB
JavaScript
39 lines
1.1 KiB
JavaScript
// zip two arrays
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export function zip(a, b) {
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return a.map((k, i) => [k, b[i]]);
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}
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export function capitalizeFirstLetter(val) {
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return String(val).charAt(0).toUpperCase() + String(val).slice(1);
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}
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const _mapRecursiveStructure = mapping => transform => root => {
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const found = mapping.get(root);
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if (found) {
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// already mapped
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// return existing result to prevent endless recursion
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return found;
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}
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// note the indirection (wrapped in lamda), this allows the user to recursively map the children (which may refer to the root) without yet having finished mapping the root.
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let memo;
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const result = () => {
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// memoization is necessary for correctness
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return memo || (memo = transform(root, _mapRecursiveStructure(mapping)(transform)));
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};
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mapping.set(root, result);
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return result;
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};
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export const mapRecursiveStructure = _mapRecursiveStructure(new Map());
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export const memoize = callback => {
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let called = false
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let result;
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return () => {
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if (!called) {
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result = callback();
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called = true;
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}
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return result;
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};
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};
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