@quenk/match NPM

Match

Runtime pattern matching for ECMAScript.

Installation

  npm install --save @quenk/match

Usage

match exports a single function match as well as two classes UnMatchedResult and MatchedResult (See typescript for interface).

match constructs a new UnMatchedResult with the value provided, use the caseOf to test the shape of the value or the orElse method for the default case.

Complete the pattern matching by calling the end() method which will return the final value (after applying any matching functions).

If none of the matches succeed an error will be thrown.

Example

  import {match} from '@quenk/match';

  class CLA {}
  class CLB {}
  class CLC {}

  // result is 3
  let result = 
    match(new CLC())
      .caseOf(CLA, (v:CLA)=> 1)
      .caseOf(CLB, (v:CLB)=> 2)
      .caseOf(CLC, (v:CLC)=> 3)
      .end();

  // result is 24
  let result = 
    match(12)
      .caseOf(CLA, (v:CLA)=> 1)
      .caseOf(CLB, (v:CLB)=> 2)
      .caseOf(CLC, (v:CLC)=> 3)
      .orElse((n:number)=> n * 2)
      .end();

  // throws an error
  let result =
    match(new Date())
      .caseOf(Array, (n:Array)=> n.length)
      .end();

For more information on the pattern matching process see the kindof library.