Validation Cheat Sheet

Use one complete predicate for requirements that must all hold. See parameter validation for the pinned implementation’s chaining behavior and helper limitations.

Basic _$() Syntax

var name = _$("Alice", "name").isString().$_();
var label = _$(undefined, "label").isString().default("Untitled");
var number = _$("42", "number").toNumber().check(v => isFinite(v)).$_();

.$_() requires a value; .default(fallback) permits an undefined value. Both return the final value. An invalid defined value still throws. Do not chain after either terminal call.

Type Validators

Requirement	Builder method
String, number, boolean	`isString()`, `isNumber()`, `isBoolean()`
Array or map	`isArray()`, `isMap()`
Date, function, regex	`isDate()`, `isFunction()`, `isRegExp()`
Object or instance	`isObject()`, `isInstanceOf(Type)`
Java object	`isJavaObject()`
Required value	Terminal `.$_()`
Optional value	Terminal `.default(value)`

Global isDef(value) / isUnDef(value) are presence tests, not builder methods.

Value Constraints

Requirement	One predicate
Specific value	`.check(v => v === "active")`
Non-empty string	`.check(v => isString(v) && v.length > 0)`
Integer port	`.check(v => isNumber(v) && Math.floor(v) === v && v >= 1 && v <= 65535)`
Username pattern	`.check(v => isString(v) && /^[a-zA-Z0-9_]{3,20}$/.test(v))`
Scalar enum	`.check(v => isString(v) && ["info", "warn", "error"].indexOf(v) >= 0)`
UUID	`.check(v => isUUID(v))`

The regex helper is regexp(/pattern/). There are no builder methods named match or inRange.

Type Conversion

Conversions return the builder. Finish with .$_() or .default(...):

var n = _$("10", "n").toNumber().check(v => isFinite(v)).$_();
var s = _$(10, "s").toString().$_();
var b = _$("true", "b").toBoolean().$_();
var d = _$("2026-11-05", "d").toDate().$_();
var a = _$("a, b", "a").toArray().$_();
var m = _$(' {"a":1} ', "m").toMap().$_();

Default Values

var timeout = _$(undefined, "timeout").isNumber().default(30000);
var config = _$(undefined, "config").isMap().default({ host: "localhost" });

Common Patterns

function validUsername(value) {
  return _$(value, "username")
    .check(v => isString(v) && /^[a-zA-Z0-9_]{3,20}$/.test(v), "invalid username")
    .$_();
}

oJob Validation Syntax

jobs:
- name: Validate request
  check:
    in:
      username: 'check(v => isString(v) && /^[a-zA-Z0-9_]{3,20}$/.test(v))'
      port: 'toNumber.check(v => isNumber(v) && v >= 1 && v <= 65535).default(8080)'
      role: 'check(v => isString(v) && ["user","admin"].indexOf(v) >= 0).default("user")'
    out:
      total: 'check(v => isNumber(v) && v >= 0)'
  exec: |
    args.total = 0;

The expression input is v. Validate array elements explicitly in job code. See the complete runnable calculation example.

Error Messages

try {
  _$(15, "age").check(v => isNumber(v) && v >= 18, "You must be 18 or older").$_();
} catch (e) {
  printErr(String(e));
}