69 lines
1.7 KiB
Markdown
69 lines
1.7 KiB
Markdown
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<p align=center>
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AssertionError and AssertionResult classes.
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</p>
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<p align=center>
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<a href="https://github.com/chaijs/assertion-error/actions">
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<img
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alt="build:?"
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src="https://github.com/chaijs/assertion-error/actions/workflows/nodejs.yml/badge.svg"
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/>
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</a><a href="https://www.npmjs.com/package/assertion-error">
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<img
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alt="downloads:?"
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src="https://img.shields.io/npm/dm/assertion-error.svg"
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/>
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</a><a href="">
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<img
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alt="devDependencies:none"
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src="https://img.shields.io/badge/dependencies-none-brightgreen"
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/>
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</a>
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</p>
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## What is AssertionError?
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Assertion Error is a module that contains two classes: `AssertionError`, which
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is an instance of an `Error`, and `AssertionResult` which is not an instance of
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Error.
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These can be useful for returning from a function - if the function "succeeds"
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return an `AssertionResult` and if the function fails return (or throw) an
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`AssertionError`.
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Both `AssertionError` and `AssertionResult` implement the `Result` interface:
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```typescript
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interface Result {
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name: "AssertionError" | "AssertionResult";
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ok: boolean;
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toJSON(...args: unknown[]): Record<string, unknown>;
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}
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```
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So if a function returns `AssertionResult | AssertionError` it is easy to check
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_which_ one is returned by checking either `.name` or `.ok`, or check
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`instanceof Error`.
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## Installation
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### Node.js
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`assertion-error` is available on [npm](http://npmjs.org).
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```
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$ npm install --save assertion-error
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```
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### Deno
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`assertion_error` is available on
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[Deno.land](https://deno.land/x/assertion_error)
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```typescript
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import {
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AssertionError,
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AssertionResult,
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} from "https://deno.land/x/assertion_error@2.0.0/mod.ts";
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```
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