---
title: Form conditions
description: Show and enable fields from typed form values.
---

Create conditions through the form whose action defines the input type.
`form.when(path)` selects a typed path from current form values. The path can
include group keys and array indexes. `form.ref(path)` reads another value
on the right side of a comparison.

<BacklitExample path="form/conditions" view="create" />

A field has `revealWhen(condition)` and `enableWhen(condition)`. These methods
return configured copies. Keep or place the returned field.
Panels, sections, form field blocks, and repeaters support `revealWhen`.
Only fields support `enableWhen`.

Conditions run in the client. They do not replace action validation or server
authorization. Hidden fields are removed from the form. Disabled fields do not
submit values. Make the action schema accept these omissions when required.

## Operators

The selected path type determines the available operators.

| Value                   | Operators                                                                                          |
| ----------------------- | -------------------------------------------------------------------------------------------------- |
| Any value               | `isMissing`, `isPresent`, `isNull`, `isNotNull`, `isEmpty`, `isNotEmpty`, `isFilled`, `isUnfilled` |
| String, number, boolean | `equals`, `doesNotEqual`, `isOneOf`, `isNoneOf`                                                    |
| String or number        | `isGreaterThan`, `isAtLeast`, `isLessThan`, `isAtMost`, `isBetween`                                |
| String                  | `containsText`, `startsWith`, `endsWith`                                                           |
| String or array         | `lengthEquals`, `lengthIsGreaterThan`, `lengthIsAtLeast`, `lengthIsLessThan`, `lengthIsAtMost`     |
| Array of scalars        | `contains`, `containsAny`, `containsAll`                                                           |
| Array of objects        | `some`, `every`, `none` with a row condition callback                                              |

`isBetween(lower, upper)` includes both bounds. Combine conditions with
`form.all(first, ...rest)`, `form.any(first, ...rest)`, or
`form.none(first, ...rest)`. Each group requires at least one condition.
For an array of objects, the callback receives paths relative to each row.
Repeaters also provide a row condition composer. See [Repeaters](/reference/forms/repeater).

A missing value is `undefined`; a null value is `null`. Empty text and empty
arrays are empty. `isFilled` requires a value that is present, non-null, and
not empty. The values `0` and `false` are filled.