type-guard

type-guard performs a runtime check that guarantees the type and value of properties in some scopes.

In a Domain Driven Design approach, it is very useful to check constraints on Domain Entity and ValueType properties.

It relies on Tyr to:

1. Call a specific Guard like string(), number().
2. Call chained rule checkers.
3. Return a GuardResult instance containing the reason for the failure of the guard, or a success.

It also relies on GuardResultBulk to manage multiple Tyr invocations:

• Combine and return the first GuardResult instance in failure, or only a GuardResult instance in success.
• Stack and return all GuardResult instances in failure, or only a GuardResult instance in success.

Table of Contents

1. Installation
2. Tyr
   1. array()
   2. boolean()
   3. class()
   4. dateString()
   5. nil()
   6. number()
   7. string()
3. Simple examples
4. Bulk Examples
5. Codex
6. TypeDoc

Installation

npm install @xtitusx/type-guard

Tyr

In order to check and return a GuardResult instance, just invoke Tyr, call a specific Guard, and finish by calling guard() method which contains the property value and optionaly a property name.

• Example of a simple type property check:

Tyr.string().guard("foo");

• Example of multiple chained rule checkers:

Tyr.string().isAlpha().contains('foo').hasMaxLength(100).isTrimmed('left').guard("Lorem ipsum foo");

Notice that only a single type of rule checker, the last called one, is retained in the guard.

So, in the following example, contains('bar') method will override contains('foo'):

Tyr.string().contains('foo').contains('bar').guard("foo");

array()

boolean()

class()

dateString()

nil()

number()

string()

Simple examples

const success: boolean = Tyr.array().hasMinSize(2).contains("foo").guard(['foo', 'bar']).isSuccess();

const success: boolean = Tyr.boolean().isTrue().guard(1 > 0).isSuccess();

const success: boolean = Tyr.class().isInstanceOf(Number).guard(new Number(1)).isSuccess();

const success: boolean = Tyr.dateString().isIso8601Date().isSameOrBefore('2016-01-20T00:00:00+02:00').guard('2015-02-28');

const success: boolean = Tyr.nil().isNil(null).guard(null).isSuccess();

const success: boolean = Tyr.number().isIn(10, 20).isEven().guard(14).isSuccess();

const success: boolean = Tyr.string().isAlpha().contains('foo').hasMaxLength(100).isTrimmed('left').guard("Lorem ipsum foo").isSuccess();

Bulk examples

const guardResult = new GuardResultBulk()
    .add([
        Tyr.array().hasMinSize(2).contains("foo").guard(['foo', 'bar'],
        Tyr.string().equals('foo').guard('foo'),
        Tyr.number().isIn(10, 20).isEven().guard(14),
    ])
    .combine();
    
const guardResult = new GuardResultBulk()
    .add([
        Tyr.array().hasMinSize(2).contains("foo").guard(['foo', 'bar'],
        Tyr.string().equals('foo').guard('foo'),
        Tyr.number().isIn(10, 20).isEven().guard(14),
    ])
    .stack();

Codex

Refer to the Codex to directly access Enums containing some ISO values:

TypeDoc

GitHub HTML Preview

Maintainer

• xtitusx - Benjamin Tussac (author)