Pattern

Pattern matching makes it possible to destructure any data (union, tuple, object, literal, predicate) and orchestrate a typed control flow thanks to match, when, otherwise, and exhaustive. Each branch returns a PatternResult, which avoids fragile switch statements, simplifies chaining with pipe, and guarantees exhaustiveness at compile time.

How to import ?

The library exposes the DPattern and P namespaces from the main entry or via direct import (tree-shaking friendly).

import { DPattern, P } from "@duplojs/utils";
import * as DPattern from "@duplojs/utils/pattern";
import * as P from "@duplojs/utils/pattern";

Running the matching

match

Associates a pattern and a transformation function. Returns a PatternResult when the input matches the pattern exactly (primitive, tuple, object, union...).

when

Adds a guard (type predicate or boolean) in a pipeline. If the condition is true, the associated function is executed and its result is wrapped.

otherwise

Defines the fallback called when no more patterns matched. Very useful to close a pipe after several when.

exhaustive

Unwraps a PatternResult to get the final value and forces TypeScript to verify that all branches have been handled.

Building and checking patterns

isMatch

Strictly tests whether a value matches a pattern and returns a type guard (value is ...). Handy for simple conditions without triggering a pipeline.

union

Composes multiple patterns into a single reusable helper (ToolPattern). Ensures the input matches one of the provided patterns (deeply on objects/arrays).