35 lines
1.1 KiB
JavaScript
35 lines
1.1 KiB
JavaScript
/*
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MIT License http://www.opensource.org/licenses/mit-license.php
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Author Tobias Koppers @sokra
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*/
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"use strict";
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/**
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* getOrInsert is a helper function for maps that allows you to get a value
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* from a map if it exists, or insert a new value if it doesn't. If it value doesn't
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* exist, it will be computed by the provided function.
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* @template K
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* @template V
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* @param {Map<K, V>} map The map object to check
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* @param {K} key The key to check
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* @param {function(): V} computer function which will compute the value if it doesn't exist
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* @returns {V} The value from the map, or the computed value
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* @example
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* ```js
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* const map = new Map();
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* const value = getOrInsert(map, "key", () => "value");
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* console.log(value); // "value"
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* ```
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*/
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module.exports.getOrInsert = (map, key, computer) => {
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// Grab key from map
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const value = map.get(key);
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// If the value already exists, return it
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if (value !== undefined) return value;
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// Otherwise compute the value, set it in the map, and return it
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const newValue = computer();
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map.set(key, newValue);
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return newValue;
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};
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