---
title: "IF Builtin"
description: "Conditional logic function for form0 expressions"
category: "logical"
tags: ["conditional", "logic", "branching"]
---

# IF Function

The `IF` builtin provides conditional logic within form0 expressions, allowing you to return different values based on a condition.

## Syntax

```javascript
IF(condition, trueValue, falseValue)
```

## Parameters

| Parameter | Type | Description |
|-----------|------|-------------|
| `condition` | `boolean` | The condition to evaluate |
| `trueValue` | `any` | Value returned when condition is true |
| `falseValue` | `any` | Value returned when condition is false |

## Return Value

Returns `trueValue` if the condition is truthy, otherwise returns `falseValue`.

## Examples

### Basic Usage

```javascript
// Show discount message based on user status
IF(user.isPremium, "20% off", "No discount")
```

### Numeric Calculations

```javascript
// Apply different tax rates
IF(country === "US", price * 0.08, price * 0.20)
```

### Nested Conditions

```javascript
// Determine shipping cost based on location and order value
IF(country === "US", 
  IF(orderValue > 50, 0, 5.99), 
  IF(orderValue > 100, 10, 15.99)
)
```

### Field Visibility

```javascript
// Show additional fields for premium users
IF(user.type === "premium", true, false)
```

### Dynamic Form Validation

```javascript
// Conditional validation messages
IF(age < 18, "Must be 18 or older", "")
```

## Common Use Cases

- **Conditional pricing**: Different prices based on user type or location
- **Dynamic field visibility**: Show/hide fields based on other field values
- **Validation messages**: Display different error messages based on conditions
- **User experience**: Personalize content based on user preferences
- **Business logic**: Implement complex conditional rules

## Best Practices

1. **Keep conditions simple**: Complex conditions can be hard to read and debug
2. **Use descriptive variable names**: Make your conditions self-documenting
3. **Consider nested IFs carefully**: Too many levels can become difficult to maintain
4. **Test edge cases**: Ensure your conditions handle all possible scenarios

## Related Functions

- [`AND`](./and.mdx) - Logical AND operations
- [`OR`](./or.mdx) - Logical OR operations

## Notes

- The condition is evaluated using JavaScript's truthiness rules
- Both `trueValue` and `falseValue` can be of any type
- The function is lazy-evaluated - only the returned branch is computed