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Module

x/result_js/mod.ts>mapErr

Minimum result type port of Rust
TomokiMiyauci/result
Latest
function mapErr
import { mapErr } from "https://deno.land/x/result_js@2.0.0/mod.ts";

Maps a Result<T, | E> to Result<T, | F> by applying fn to a contained Err value, leaving an Ok.

Examples

Example 1

import { Err, type Result } from "https://deno.land/x/result_js/spec.ts";
import { mapErr } from "https://deno.land/x/result_js/operators/transform.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

const result: Result<unknown, string> = Err("Hello, World!");
const resultLen = mapErr(result, (v) => v.length);

assertEquals(resultLen, Err(13));

Parameters

result: Result<T, E>
fn: (value: E) => F