# sarcastic > Cast unknown values to typed values Latest version **1.5.0** (published 2018-08-31) · SEE LICENSE IN LICENSE license · 0 weekly downloads ## Install ```sh npm install sarcastic pnpm add sarcastic yarn add sarcastic bun add sarcastic ``` ## Health **Score 15/100 (F)** — status: abandoned. Positive: no vulnerabilities. Warnings: low downloads; no types; no esm support. Negative: abandoned; low maintenance score. ## Facts | | | |---|---| | Version | 1.5.0 | | Published | 2018-08-31 | | First published | 2018-06-10 | | Weekly downloads | 0 | | License | SEE LICENSE IN LICENSE | | TypeScript types | none | | Module format | CommonJS | | Dependencies | 0 | | Unpacked size | 13 KB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 99 | | Author | James Kyle | | Maintainers | thejameskyle | | Keywords | type, flow, cast, assert, assertions, immutable | ## Links - npm: https://www.npmjs.com/package/sarcastic - Repository: https://github.com/jamiebuilds/sarcastic - Homepage: https://github.com/jamiebuilds/sarcastic#readme - Issues: https://github.com/jamiebuilds/sarcastic/issues - npm.io page: https://npm.io/package/sarcastic ## Alternatives - [@openai/codex-sdk](https://npm.io/package/@openai/codex-sdk.md) — 731.4K weekly downloads - [babel-plugin-transform-react-jsx](https://npm.io/package/babel-plugin-transform-react-jsx.md) — 565.0K weekly downloads - [babel-helper-remove-or-void](https://npm.io/package/babel-helper-remove-or-void.md) — 508.5K weekly downloads - [@pnpm/store-controller-types](https://npm.io/package/@pnpm/store-controller-types.md) — 186.9K weekly downloads - [react-native-signature-canvas](https://npm.io/package/react-native-signature-canvas.md) — 155.6K weekly downloads ## Recent versions - 1.5.0 (latest) — 2018-08-31 - 1.4.0 — 2018-07-17 - 1.3.0 — 2018-06-18 - 1.2.0 — 2018-06-18 - 1.1.0 — 2018-06-18 - 1.0.1 — 2018-06-10 - 1.0.0 — 2018-06-10 ## README # Sarcastic > Cast unknown values to typed values - Asserts that a value matches the defined type - Returns a typed value - Copies the value for type safety ## Install ```sh yarn add sarcastic ``` ## Usage ```js const is = require('sarcastic'); const PKG_SHAPE = is.shape({ name: is.string, version: is.string, private: is.default(is.boolean, false), scripts: is.maybe(is.objectOf(is.string)), bin: is.maybe(is.either(is.string, is.arrayOf(is.string))), }); let pkg = is(require('./package.json'), PKG_SHAPE); // { // name: "sarcastic", // version: "1.0.0", // private: false, // scripts: { "test": "ava" }, // bin: null // } ``` **With strict typing:** ```js import is, { type AssertionType } from 'sarcastic'; const PKG_SHAPE = is.shape({ name: is.string, version: is.string, private: is.maybe(is.boolean), scripts: is.maybe(is.objectOf(is.string)), bin: is.maybe(is.either(is.string, is.arrayOf(is.string))), }); type PkgShape = AssertionType; function assertPkg(pkg: mixed): PkgShape { return is(pkg, PKG_SHAPE, 'pkg'); } let pkg = assertPkg(require('./package.json')); ``` ## API ### `is(val, assertion, name?)` ```js is(true, is.boolean); ``` You can optionally pass a name for the value so that errors are more descriptive: ```js is(deepObj, deepShape, 'example'); // example.pathTo.nestedKeys.withIndexesLike[14] ``` Alternatively you can pass a formatter as the name which will receive the path to the error as strings for keys and numbers for indexes: ```js is(deepObj, deepShape, (...keyPath) => ['example', ...keyPath].join(' > ')); // example > pathTo > nestedKeys > withIndexesLike > 14 ``` ### `is.boolean` ```js is(true, is.boolean); // returns true is(false, is.boolean); // returns false is(42, is.boolean); // throws instanceof is.AssertionError ``` ### `is.number` ```js is(42, is.number); // returns 42 is(NaN, is.number); // returns NaN is(true, is.number); // throws instanceof is.AssertionError ``` ### `is.string` ```js is("", is.string); // returns "" is("hi", is.string); // returns "hi" is(true, is.string); // throws instanceof is.AssertionError ``` ### `is.array` ```js is([], is.array); // returns [] is([1, 2, 3], is.array); // returns [1, 2, 3] is({}, is.array); // throws instanceof is.AssertionError ``` ### `is.func` ```js is(() => {}, is.func); // returns () => {} is({}, is.func); // throws instanceof is.AssertionError is(/regex/, is.func); // throws instanceof is.AssertionError ``` ### `is.object` ```js is({}, is.object); // returns {} is({ foo: true }, is.object); // returns { foo: true } is([], is.object); // throws instanceof is.AssertionError is(null, is.object); // throws instanceof is.AssertionError ``` ### `is.arrayOf(assertion)` ```js is([], is.arrayOf(is.number)); // returns [] is([1, 2, 3], is.arrayOf(is.number)); // returns [1, 2, 3] is({}, is.arrayOf(is.number)); // throws instanceof is.AssertionError is(["hi"], is.arrayOf(is.number)); // throws instanceof is.AssertionError ``` ### `is.arrayish(assertion)` ```js is(1, is.arrayish(is.number)); // returns [1] is([], is.arrayish(is.number)); // returns [] is([1, 2, 3], is.arrayish(is.number)); // returns [1, 2, 3] is("hi", is.arrayish(is.number)); // throws instanceof is.AssertionError is({}, is.arrayish(is.number)); // throws instanceof is.AssertionError is(["hi"], is.arrayish(is.number)); // throws instanceof is.AssertionError ``` ### `is.objectOf(assertion)` ```js is({}, is.objectOf(is.boolean)); // returns {} is({ foo: true }, is.objectOf(is.boolean)); // returns { foo: true } is([], is.objectOf(is.boolean)); // throws instanceof is.AssertionError is(null, is.objectOf(is.boolean)); // throws instanceof is.AssertionError is({ foo: 42 }, is.objectOf(is.boolean)); // throws instanceof is.AssertionError ``` ### `is.shape({ [key: string]: assertion })` ```js let myShape = is.shape({ foo: is.boolean }); is({ foo: true }, myShape); // returns { foo: true is({ foo: true, bar: false }, myShape); // returns { foo: true } is([], myShape); // throws instanceof is.AssertionError is(null, myShape); // throws instanceof is.AssertionError is({ foo: 42 }, myShape); // throws instanceof is.AssertionError ``` ### `is.maybe(assertion)` ```js is(undefined, is.maybe(is.boolean)); // returns null is(null, is.maybe(is.boolean)); // returns null is(true, is.maybe(is.boolean)); // returns true is(42, is.maybe(is.boolean)); // throws instanceof is.AssertionError ``` ### `is.default(assertion, defaultValue)` ```js is(undefined, is.default(is.number, 42)); // returns 42 is(null, is.default(is.number, 42)); // returns 42 is(3.14, is.default(is.number, 42)); // returns 3.14 is("hi", is.default(is.number, 42)); // throws instanceof is.AssertionError ``` ### `is.either(assertionA, assertionB)` ```js is(true, is.either(is.boolean, is.string)); // returns true is("hi", is.either(is.boolean, is.string)); // returns "hi" is(42, is.either(is.boolean, is.string)); // throws instanceof is.AssertionError ``` ### `is.AssertionError` ```js try { is(true, is.number); } catch (err) { if (err instanceof is.AssertionError) { // an assertion error } else { // some other unexpected error } } ``` --- _Source: https://npm.io/package/sarcastic · Machine-readable twin of the npm.io package page. 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