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findDuplicates in an array of objects
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| const defaultOptions = { | |
| addError: <T extends { [key: string]: unknown }>( | |
| item: T, | |
| fieldName: string | |
| ) => ({ | |
| id: item.id, | |
| value: item[fieldName], | |
| }), | |
| }; | |
| /** | |
| * | |
| * @param items - array of objects to be looked at | |
| * @param fieldNames - array of string key names from the objects from the array above to check for duplicates | |
| * ``` | |
| * const duplicates = findDuplicates(items, ['name', 'email']) | |
| * | |
| * if (duplicates) { | |
| * // do something | |
| * } | |
| * ``` | |
| */ | |
| export default function findDuplicates<T extends { [key: string]: unknown }>( | |
| items: T[] = [], | |
| fieldNames: string[] = [], | |
| { addError } = defaultOptions | |
| ): undefined | Map<string, { id: number; value: unknown }> { | |
| const errors = new Map(); | |
| fieldNames.forEach((fieldName) => { | |
| const seen = new Set(); | |
| // eslint-disable-next-line array-callback-return | |
| items.some((item) => { | |
| /** if the value doesn't exist, skip it */ | |
| if (!item[fieldName]) return; | |
| /** otherwise check if size differs after insertion and add an error if it doesn't */ | |
| if (seen.size === seen.add(item[fieldName]).size) { | |
| errors.set(fieldName, addError(item, fieldName)); | |
| } | |
| }); | |
| }); | |
| return errors.size > 0 ? errors : undefined; | |
| } |
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