# Expressions SvGrid does not ship a formula / expression language for cells. Computed values are JavaScript - either via `fieldFn` or inside a `cell` callback. > Live demo: Spreadsheet + formulas - https://svgrid.com/demos/83-spreadsheet-formulas/ ## Per-cell computation ```ts { id: 'totalCost', header: 'Total', fieldFn: (row) => row.unitPrice * row.quantity, format: { type: 'currency', currency: 'USD' }, } ``` `fieldFn` runs every time the row's value is needed (display, sort, filter, copy). The result is treated as a plain value of the resulting type, so `format` / `formatter` / `editorType` all apply. ## Cross-row aggregation For computed columns that depend on **other rows** (running total, rank, delta-from-mean), do the computation **before** you pass data into the grid - derive a new array with the aggregate fields baked in: ```svelte ``` The grid's row pipeline runs **per row** - it does not give you a hook for "emit a derived column that needs the whole array". ## Formula language A spreadsheet-style formula language (cells like `=A1+B2`) is **not** in the SvGrid community build. There is no formula parser or formula editor. If you need spreadsheet-style cells, that's a separate library - wire its output into a column's `fieldFn`. ## A computed column with fieldFn Because `fieldFn` produces the value the rest of the pipeline sees, the computed column sorts and filters like a stored one. Give it an `id` - a column's id is its `field` unless you say otherwise, and a `fieldFn` column has no field to fall back on. ```svelte ``` ## The cross-row case, done before the grid sees it Share-of-total needs every row, and the row pipeline only ever hands you one. So compute it in a `$derived` over the array and pass the result down. Sorting by that column then works for free, because by the time the grid sees it, it is an ordinary number. ```svelte ``` ## See also - [Column definitions](https://svgrid.com/docs/help/columns/column-definitions/) - [Server-side guide](https://svgrid.com/docs/getting-started/#11-server-side-data) - for aggregates the server is better at than the client. --- SvGrid is the Svelte 5 data grid (`npm install @svgrid/grid`, MIT). This page: https://svgrid.com/docs/help/cells/expressions/ . All docs: https://svgrid.com/llms.txt