Patterns

Patterns are proven solutions to common configuration problems. Use them to write cleaner, more maintainable JSSON.

Data Generation

Use Ranges for Scale

When you need many similar items, ranges are your best friend.

//  Good: Generate 100 users with a range
users = 1..100 map (id) = { id = id, name = "User " + id }

//  Bad: Manually specifying each
users = [
  { id = 1, name = "User 1" },
  { id = 2, name = "User 2" },
  // ... 98 more times
]

When to use: Database seeding, test fixtures, mock data, bulk configuration.

Use Templates for Structured Data

When rows have a fixed structure, templates make the code readable.

//  Good: Clear column headers
users [
  template { name, email, role }
  
  "Alice", "alice@example.com", "admin"
  "Bob", "bob@example.com", "user"
]

//  Bad: Anonymous tuples are confusing
users = [
  ["Alice", "alice@example.com", "admin"],
  ["Bob", "bob@example.com", "user"]
]

When to use: User lists, feature flags, environment configs.

Reusability

Use Presets for Shared Defaults

Extract common properties into presets to avoid duplication.

//  Good: DRY with presets
@preset "apiDefaults" {
  timeout = 30
  retries = 3
  ssl = yes
}

authService = @use "apiDefaults" { endpoint = "/auth" }
paymentService = @use "apiDefaults" { endpoint = "/payment", timeout = 60 }

//  Bad: Duplicated values
authService = { timeout = 30, retries = 3, ssl = yes, endpoint = "/auth" }
paymentService = { timeout = 60, retries = 3, ssl = yes, endpoint = "/payment" }

When to use: Shared defaults, component configs, multi-environment setups.

Override Selectively

Presets allow you to override only what's different.

@preset "logDefaults" {
  level = "info"
  format = "json"
  output = "stdout"
}

prodLogs = @use "logDefaults" { level = "error" }
devLogs = @use "logDefaults" { level = "debug", output = "file" }

Conditional Logic

Use Ternaries for Environment Switching

env := "prod"

config {
  database = env == "prod" ? "db.example.com" : "localhost"
  debug = env == "dev" ? yes : no
  replicas = env == "prod" ? 5 : 1
}

When to use: Environment-specific values that differ by a single variable.

Use Map with Conditions for Complex Logic

users [
  template { id, plan }
  
  map (u) = {
    id = u.id
    storage = u.plan == "pro" ? 100 : (u.plan == "team" ? 500 : 10)
    features = u.plan == "free" ? ["basic"] : ["basic", "advanced"]
  }
  
  1, "free"
  2, "pro"
  3, "team"
]

Validators

Use Validators for Realistic Mock Data

//  Good: Auto-generated realistic data
users [
  template { role }
  map (u) = {
    id = @uuid
    email = @email
    createdAt = @datetime
    role = u.role
  }
  "admin", "user", "user"
]

//  Bad: Manual fake data
users = [
  { id = "1", email = "a@b.com", createdAt = "2025-01-01" }
]

When to use: Test data, database seeding, API mocking.

Modularity

Split Large Files with Include

// main.jsson
include "database.jsson"
include "api.jsson"
include "features.jsson"

When to use: Projects with 100+ lines of config, team environments.

//  Good: Grouped by concern
config {
  database { host = "localhost", port = 5432 }
  cache { host = "localhost", port = 6379 }
  api { port = 8080, timeout = 30 }
}

//  Bad: Flat namespace
databaseHost = "localhost"
databasePort = 5432
cacheHost = "localhost"
cachePort = 6379

Naming

Use Descriptive Preset Names

//  Good
@preset "httpServiceDefaults" { ... }
@preset "databaseConnectionPool" { ... }

//  Bad
@preset "defaults" { ... }
@preset "config1" { ... }

Use Semantic Boolean Names

//  Good: Clear intent
enabled = yes
debugMode = on
requiresAuth = yes

//  Avoid: Ambiguous  
flag = true
mode = 1

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