---
name: jsonlogic-validator
description: Implement, validate, and test JSONLogic rules for portable business logic. Use when working with JSONLogic syntax, creating rules for conditional logic, validating rule structures, testing rules against data, or converting business requirements to JSONLogic. Triggers on requests to "write jsonlogic", "validate jsonlogic", "create a rule", "business logic as JSON", "conditional logic", or any mention of JSONLogic rules.
---

# JSONLogic Validator

Implement and validate JSONLogic rules—portable, JSON-serializable business logic that works across JavaScript, Python, PHP, Ruby, Go, Java, .Net, and C++.

## Core Syntax

Every rule: `{ "operator": [arguments] }`

```json
{"==": [1, 1]}                              // comparison
{"var": "user.name"}                        // data access
{"and": [{">=": [{"var": "age"}, 18]}, {"var": "active"}]}  // compound
```

## Quick Reference

| Category | Operators |
|----------|-----------|
| **Data** | `var`, `missing`, `missing_some` |
| **Logic** | `if`, `==`, `===`, `!=`, `!==`, `!`, `!!`, `and`, `or` |
| **Numeric** | `>`, `>=`, `<`, `<=`, `+`, `-`, `*`, `/`, `%`, `max`, `min` |
| **Array** | `map`, `filter`, `reduce`, `all`, `some`, `none`, `merge`, `in` |
| **String** | `cat`, `substr`, `in` |

## Workflow

### 1. Gather Requirements

Clarify:
- What data fields are available?
- What conditions determine the outcome?
- What should the rule return (boolean, value, category)?

### 2. Write the Rule

Build incrementally from inner expressions outward:

```json
// Requirement: "Premium users over 25 get 20% discount, others get 10%"
{
  "if": [
    {"and": [
      {"==": [{"var": "tier"}, "premium"]},
      {">": [{"var": "age"}, 25]}
    ]},
    0.20,
    0.10
  ]
}
```

### 3. Validate

Run the validation script (no dependencies required):

```bash
node scripts/validate-jsonlogic.js '<rule>' '<data>'
```

Example:
```bash
node scripts/validate-jsonlogic.js '{">=": [{"var": "age"}, 18]}' '{"age": 25}'
```

### 4. Test with Cases

Requires: `npm install json-logic-js`

```bash
node scripts/test-jsonlogic.js '<rule>' --test-cases '[
  {"data": {"age": 25}, "expected": true},
  {"data": {"age": 15}, "expected": false}
]'
```

## Common Patterns

### Null-safe access with default
```json
{"var": ["user.name", "Guest"]}
```

### Range check (between)
```json
{"<=": [0, {"var": "value"}, 100]}
```

### Multi-condition (all must pass)
```json
{"and": [
  {">=": [{"var": "age"}, 18]},
  {"==": [{"var": "status"}, "active"]},
  {"in": [{"var": "role"}, ["admin", "editor"]]}
]}
```

### Grade/tier classification
```json
{"if": [
  {">=": [{"var": "score"}, 90]}, "A",
  {">=": [{"var": "score"}, 80]}, "B",
  {">=": [{"var": "score"}, 70]}, "C",
  "F"
]}
```

### Array operations
```json
// Sum: reduce with +
{"reduce": [{"var": "items"}, {"+": [{"var": "accumulator"}, {"var": "current"}]}, 0]}

// Filter: keep matching
{"filter": [{"var": "items"}, {">": [{"var": ""}, 10]}]}

// Any match: some
{"some": [{"var": "items"}, {"==": [{"var": ".status"}, "error"]}]}
```

## Truthy/Falsy (differs from JavaScript)

**Falsy**: `0`, `[]`, `""`, `null`
**Truthy**: Everything else (including `"0"` and `[0]`)

## Validation Checklist

Before deploying a rule:

- [ ] Valid JSON syntax
- [ ] All operators spelled correctly
- [ ] Arguments in arrays where required
- [ ] Data paths match actual data structure
- [ ] Edge cases handled (null, empty, missing keys)
- [ ] Tested with representative data samples

## References

For complete operator documentation with all arguments and edge cases:
- See `references/jsonlogic-reference.md`