Custom Data Types and Performance Considerations

import LightningDatatable from 'lightning/datatable';
import statusBadgeTemplate from './statusBadge.html';

export default class CustomDatatable extends LightningDatatable {
    static customTypes = {
        statusBadge: {
            template: statusBadgeTemplate,
            typeAttributes: ['status'],
        },
    };
}

For rendering something text/currency/date can't express — like a colored status badge — extend LightningDatatable itself and register a customTypes entry pointing to your own cell template. The extended class is then used in markup exactly like lightning-datatable, just under its own custom tag name.

• Don't recreate the columns array on every render. Defining columns as a plain class field (set once) rather than recomputing it inside a getter avoids the datatable treating it as "changed" unnecessarily on every re-render.
• Hide the checkbox column when selection isn't needed (hide-checkbox-column) — a small but real reduction in per-row rendering work.
• Paginate rather than rendering everything. Even with fast client-side filtering, rendering thousands of DOM rows at once is genuinely slow — Lesson 3's pagination patterns exist for this reason too, not just server load.

A datatable that feels instant with 20 test rows can feel sluggish with 2,000 real ones if these considerations are ignored — exactly the kind of "works in the demo, slow in production" gap Module 7's governor-limits lesson warned about for Apex, now showing up on the client side instead.