#unwrapOr

Extract the value from an Ok, or return a fallback for an Err. Unlike unwrap, failure does not throw. Mirrors Rust's Result::unwrap_or.

#Usage

#unwrapOr(result, fallback)

import { err, ok, unwrapOr } from 'massaman/control'

unwrapOr(ok(42), 0)      // 42
unwrapOr(err('bad'), 0)  // 0
unwrapOr(ok(null), 0)    // null
unwrapOr(ok(false), true) // false

This checks the Result's ok discriminant, not the truthiness of its value. Successful null, undefined, false, 0, and empty strings are preserved.

#Parameters

#Returns

T | U, not a Result. Values are returned by reference. Function values are returned, never invoked.

#Eager fallback evaluation

JavaScript evaluates the fallback expression before calling unwrapOr, even on success:

unwrapOr(ok(42), computeDefault()) // computeDefault runs too.

Prefer literals or already-computed defaults. For conditional recovery work, use orElse(result, () => ok(computeDefault())). If evaluating the fallback throws, the exception occurs before unwrapOr runs.

#See also

• unwrap — throw on failure instead
• orElse — perform recovery only on failure
• Result & Errors