# Duplicate guard A React component in [Beamline](https://beamline.io/)'s [Data & tables](https://beamline.io/components/data) category. Live demo: https://beamline.io/components/duplicate-guard A new record that watches for the one that already exists: as you type, the likely duplicates slide in beside the form with the fields that match lit and said in words (Number plate · same, Name · similar), strongest first. Use the existing record, merge what you typed into it (both fold into one column, agreements read once, every difference a choice with the existing value first, nothing lost) or say Not them; Create stays offered and becomes the main action when nothing matches. ## Use it for - Creating a customer, contact, patient, member or vehicle where the same one may already exist under another spelling: garages, clinics, help desks, CRMs, school offices. - The host passes the records to look in (or the ones its own search found) and owns what Use, Merge and Create do; the part compares, explains and builds the merged values. ## Not for - Mapping columns of an imported file to fields → [import-mapping](https://beamline.io/components/import-mapping); fixing an imported file's rows → [import-lens](https://beamline.io/components/import-lens). - Searching a list to pick one item → combobox or command-palette. ## Anatomy - form: the label, one field per GuardField; a field that matches a shown card carries a lit mark; Create {name} (Create new while no name) - matches: Possible matches; up to three cards, strongest first; a card: the record's name and detail, its reasons as chips (same filled, similar outlined), Use / Merge / Not them; and N more possible - merge (inside its card): What {name} will have, one row per field: Same in both, kept, from what you typed, or a choice of two (the existing value first); Merge into {name} / Cancel - done: Merged into / Created / Using {name} ## States - empty - typing (matches arrive) - a match (same) - a match (similar) - more than three - merging - a card put aside - no matches - merged - created - used ## Keyboard - The fields are ordinary inputs; each card is a region named by its record and Tab reaches Use, Merge and Not them - In the merge, each difference is a radio group of two; Escape closes the merge and returns to the card's Merge - Not them moves focus to the next card's first action, or to Create; arriving matches are said once (a polite status) ## Motion A card slides in where it belongs, moves when it rises past another, and leaves as a ghost; the merge rows grow out of the reason chips they came from (the shared FLIP). A field's lit mark grows in. Nothing runs at rest; reduced motion places everything. ## Props | Prop | Type | Default | Description | | --- | --- | --- | --- | | `label` (required) | `string` | — | What is being created: "New customer". | | `fields` (required) | `GuardField[]` | — | | | `records` (required) | `GuardRecord[]` | — | The records to look in (the host may pass the ones its own search found). | | `value` | `Record` | — | The draft, by field id. | | `defaultValue` | `Record` | — | Initial selection when uncontrolled; omitted by default. | | `onValueChange` | `((draft: Record) => void)` | — | Reports the selected value after a change; no callback by default. | | `onUse` | `((record: GuardRecord) => void)` | — | Use an existing record instead of creating one (the host keeps the draft for it if it likes). | | `onMerge` | `((record: GuardRecord, merged: Record) => void \| Promise)` | — | Merge what was typed into a record: the combined values, every difference chosen. | | `onCreate` | `((draft: Record) => void \| Promise)` | — | Create the new record (always offered). | | `match` | `((draft: Record, record: GuardRecord) => GuardReason[])` | — | Replace the built-in comparison: the reasons a record matches the draft (none: not a match). | | `limit` | `number` | — | How many cards at most; the rest are counted. Default 3. | | `className` | `string` | — | Classes on the documented visual root; no override by default. | | `classNames` | `Partial>` | — | Classes for the named visual parts; no overrides by default. | | `style` | `CSSProperties` | — | Inline styles on the documented visual root; no overrides by default. | | `ref` | `Ref` | — | Receives the documented native target or imperative handle; omitted by default. | ## Built from - [Avatar](https://beamline.io/components/avatar.md) - [Button](https://beamline.io/components/button.md) - [Input](https://beamline.io/components/input.md) - [Label](https://beamline.io/components/label.md) - [Spinner](https://beamline.io/components/spinner.md) ## Dependencies `lucide-react` ## Import ```tsx import { DuplicateGuard } from "@beamline/duplicate-guard"; ``` ## Get it Duplicate guard is part of Beamline UI. Install the parts you need in your React app as compiled packages or editable source. [Get Beamline](https://beamline.io/checkout?pack=complete) · [Connect your agent](https://beamline.io/connect) ## More in Data & tables - [Living table](https://beamline.io/components/living-table): A table that shows as much as fits on both axes: width decides which columns show (the rest ride in the name line, moving there rather than vanishing)… - [Availability layers](https://beamline.io/components/availability-layers): A week of bookable start times whose closed times explain themselves: every availability rule (hours, time off, bookings, buffers, rooms, lead time… - [Capacity terrain](https://beamline.io/components/capacity-terrain): A schedule that stands on a terrain of capacity: under each station's lane of jobs, every day's load rises to its capacity line and an overload is a… - [Domino move](https://beamline.io/components/domino-move): A room board where one move shows its chain: drag a booking (or pick it and aim it with the keys) onto a taken room and the bookings it would push appear… - [Match board](https://beamline.io/components/match-board): Month-end matching as one picture: bank lines and books entries side by side with threads between them — solid for matched, dashed with the host's reason… - [Split anything](https://beamline.io/components/split-anything): One splitter for money, quantities and time: a bar of the whole shows every target's part and what is not split yet; 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