Tsertion

Low level type guards and assertions for typescript.

Install

npm install tsertion

Usage

import { assertString, getObject, getArray, getNumber } from 'tsertion';

const a: unknown = 'foo';
const b: unknown = null;
const c: unknown = [1, 2, 3];

assertString(a, 'a');

console.log(a.trim());
console.log(getObject(b, 'b').foo); // throws a runtime type error
console.log(
  getArray(c, 'c')
    .map(value => getNumber(value))
    .reduce((a, b) => a + b, 0)
);

API

string

assertString(value: unknown, name?: string): asserts value is string

Throws if value isn't a string.

assertStringOptional(value: unknown, name?: string): asserts value is (string | undefined)

Throws if value isn't a string or undefined.

assertStringNullable(value: unknown, name?: string): asserts value is (string | null)

Throws if value isn't a string or null.

assertStringOptionalNullable(value: unknown, name?: string): asserts value is (string | undefined | null)

Throws if value isn't a string or undefined. or null.

getString(value: unknown, name?: string): string

Throws if value isn't a string. Otherwise returns value.

getStringOptional(value: unknown, name?: string): string | undefined

Throws if value isn't a string or undefined. Otherwise returns value.

getStringNullable(value: unknown, name?: string): string | null

Throws if value isn't a string or null. Otherwise returns value.

getStringOptionalNullable(value: unknown, name?: string): string | undefined | null

Throws if value isn't a string or undefined. Otherwise returns value.

number

assertNumber(value: unknown, name?: string): asserts value is number

Throws if value isn't a number.

assertNumberOptional(value: unknown, name?: string): asserts value is (number | undefined)

Throws if value isn't a number or undefined.

assertNumberNullable(value: unknown, name?: string): asserts value is (number | null)

Throws if value isn't a number or null.

assertNumberOptionalNullable(value: unknown, name?: string): asserts value is (number | undefined | null)

Throws if value isn't a number or undefined. or null.

getNumber(value: unknown, name?: string): number

Throws if value isn't a number. Otherwise returns value.

getNumberOptional(value: unknown, name?: string): number | undefined

Throws if value isn't a number or undefined. Otherwise returns value.

getNumberNullable(value: unknown, name?: string): number | null

Throws if value isn't a number or null. Otherwise returns value.

getNumberOptionalNullable(value: unknown, name?: string): number | undefined | null

Throws if value isn't a number or undefined. Otherwise returns value.

boolean

assertBoolean(value: unknown, name?: string): asserts value is boolean

Throws if value isn't a boolean.

assertBooleanOptional(value: unknown, name?: string): asserts value is (boolean | undefined)

Throws if value isn't a boolean or undefined.

assertBooleanNullable(value: unknown, name?: string): asserts value is (boolean | null)

Throws if value isn't a boolean or null.

assertBooleanOptionalNullable(value: unknown, name?: string): asserts value is (boolean | undefined | null)

Throws if value isn't a boolean or undefined. or null.

getBoolean(value: unknown, name?: string): boolean

Throws if value isn't a boolean. Otherwise returns value.

getBooleanOptional(value: unknown, name?: string): boolean | undefined

Throws if value isn't a boolean or undefined. Otherwise returns value.

getBooleanNullable(value: unknown, name?: string): boolean | null

Throws if value isn't a boolean or null. Otherwise returns value.

getBooleanOptionalNullable(value: unknown, name?: string): boolean | undefined | null

Throws if value isn't a boolean or undefined. Otherwise returns value.

object

assertObject(value: unknown, name?: string): asserts value is Record<any, unknown>

Throws if value isn't an object.

assertObjectOptional(value: unknown, name?: string): asserts value is (Record<any, unknown> | undefined)

Throws if value isn't an object or undefined.

assertObjectNullable(value: unknown, name?: string): asserts value is (Record<any, unknown> | null)

Throws if value isn't an object or null.

assertObjectOptionalNullable(value: unknown, name?: string): asserts value is (Record<any, unknown> | undefined | null)

Throws if value isn't an object or undefined. or null.

getObject(value: unknown, name?: string): Record<any, unknown>

Throws if value isn't an object. Otherwise returns value.

getObjectOptional(value: unknown, name?: string): Record<any, unknown> | undefined

Throws if value isn't an object or undefined. Otherwise returns value.

getObjectNullable(value: unknown, name?: string): Record<any, unknown> | null

Throws if value isn't an object or null. Otherwise returns value.

getObjectOptionalNullable(value: unknown, name?: string): Record<any, unknown> | undefined | null

Throws if value isn't an object or undefined. Otherwise returns value.

array

assertArray(value: unknown, name?: string): asserts value is unknown[]

Throws if value isn't an array.

assertArrayOptional(value: unknown, name?: string): asserts value is (unknown[] | undefined)

Throws if value isn't an array or undefined.

assertArrayNullable(value: unknown, name?: string): asserts value is (unknown[] | null)

Throws if value isn't an array or null.

assertArrayOptionalNullable(value: unknown, name?: string): asserts value is (unknown[] | undefined | null)

Throws if value isn't an array or undefined. or null.

getArray(value: unknown, name?: string): unknown[]

Throws if value isn't an array. Otherwise returns value.

getArrayOptional(value: unknown, name?: string): unknown[] | undefined

Throws if value isn't an array or undefined. Otherwise returns value.

getArrayNullable(value: unknown, name?: string): unknown[] | null

Throws if value isn't an array or null. Otherwise returns value.

getArrayOptionalNullable(value: unknown, name?: string): unknown | undefined | null

Throws if value isn't an array or undefined. Otherwise returns value.