23 lines
421 B
JavaScript
23 lines
421 B
JavaScript
// utilities for working with Maps
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export function mapBy (items, func) {
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const map = new Map()
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for (const item of items) {
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map.set(func(item), item)
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}
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return map
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}
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export function multimapBy (items, func) {
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const map = new Map()
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for (const item of items) {
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const key = func(item)
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if (map.has(key)) {
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map.get(key).push(item)
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} else {
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map.set(key, [item])
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}
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}
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return map
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}
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