33 lines
1 KiB
TypeScript
33 lines
1 KiB
TypeScript
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// Copyright 2020 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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import { has } from 'lodash';
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/**
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* This function is like `Object.assign` but won't create a new object if we don't need
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* to. This is purely a performance optimization.
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*
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* This is useful in places where we don't want to create a new object unnecessarily,
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* like in reducers where we might cause an unnecessary re-render.
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*
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* See the tests for the specifics of how this works.
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*/
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// We want this to work with any object, so we allow `object` here.
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// eslint-disable-next-line @typescript-eslint/ban-types
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export function assignWithNoUnnecessaryAllocation<T extends object>(
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obj: Readonly<T>,
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source: Readonly<Partial<T>>
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): T {
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// We want to bail early so we use `for .. in` instead of `Object.keys` or similar.
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// eslint-disable-next-line no-restricted-syntax
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for (const key in source) {
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if (!has(source, key)) {
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continue;
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}
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if (!(key in obj) || obj[key] !== source[key]) {
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return { ...obj, ...source };
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}
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}
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return obj;
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}
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