shelving/util/booleanmodule

Type guards and assertion functions for boolean values. These follow the standard is* / assert* naming convention and pair naturally with schema validation and runtime checks.

Usage

Type guards

ts
import { isBoolean, isTrue, isFalse, isTruthy, isFalsey } from "shelving/util";

isBoolean(true);   // true
isBoolean(1);      // false  — 1 is not a boolean
isTrue(true);      // true
isFalse(false);    // true
isTruthy("hello"); // true  — any truthy value
isFalsey(0);       // true  — any falsy value

Assertions

ts
import { assertBoolean, assertTrue, assertFalse, assertTruthy, assertFalsy } from "shelving/util";

assertBoolean(value);  // throws RequiredError if not a boolean
assertTrue(value);     // throws RequiredError if not exactly true
assertFalse(value);    // throws RequiredError if not exactly false
assertTruthy(value);   // throws RequiredError if falsy
assertFalsy(value);    // throws RequiredError if truthy

Functions

Go

isBoolean()function

Is an unknown value a boolean?

isBoolean(value: unknown): value is boolean
Go

isTrue()function

Is an unknown value exactly true?

isTrue(value: unknown): value is true
Go

isFalse()function

Is an unknown value exactly false?

isFalse(value: unknown): value is false
Go

isTruthy()function

Is an unknown value truthy?

isTruthy(value: unknown): boolean
Go

isFalsey()function

Is an unknown value falsey?

isFalsey(value: unknown): boolean
Go

assertBoolean()function

Assert that an unknown value is a boolean.

assertBoolean(value: unknown, caller: AnyCaller = assertBoolean): asserts value is boolean
Go

assertTrue()function

Assert that an unknown value is exactly true.

assertTrue(value: unknown, caller: AnyCaller = assertTrue): asserts value is true
Go

assertFalse()function

Assert that an unknown value is exactly false.

assertFalse(value: unknown, caller: AnyCaller = assertFalse): asserts value is false
Go

assertTruthy()function

Assert that an unknown value is truthy.

assertTruthy(value: unknown, caller: AnyCaller = assertTruthy): asserts value is true
Go

assertFalsy()function

Assert that an unknown value is falsy.

assertFalsy(value: unknown, caller: AnyCaller = assertFalsy): asserts value is false