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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
const mergeCache = new WeakMap();
/**
* Merges two given objects and caches the result to avoid computation if same objects passed as arguments again.
* @example
* // performs Object.assign(first, second), stores the result in WeakMap and returns result
* cachedMerge({a: 1}, {a: 2})
* {a: 2}
* // when same arguments passed, gets the result from WeakMap and returns it.
* cachedMerge({a: 1}, {a: 2})
* {a: 2}
* @param {object} first first object
* @param {object} second second object
* @returns {object} merged object of first and second object
*/
const cachedMerge = (first, second) => {
let innerCache = mergeCache.get(first);
if (innerCache === undefined) {
innerCache = new WeakMap();
mergeCache.set(first, innerCache);
}
const prevMerge = innerCache.get(second);
if (prevMerge !== undefined) return prevMerge;
const newMerge = Object.assign({}, first, second);
innerCache.set(second, newMerge);
return newMerge;
};
module.exports = cachedMerge;