DevisPattern

An exact-match pattern matcher on JavaScript object properties.

This module is used by the devis framework to route actions to their handlers.

Since 2.0.0 it is plain JavaScript: no compiler, CMake or native build is needed. Node.js 22 or later is required.

Install

npm install devisPattern

Quick example

const DevisPattern = require("devisPattern");
const devisPattern = new DevisPattern();

devisPattern.add({
    action: "game",
    cmd: "play"
}, (args, done) => {
    done({
        result: "play"
    });
});

devisPattern.call({
    action: "game",
    cmd: "play"
}, (result) => {
    console.log(result); // { result: 'play' }
});

Matching rules

A pattern matches only an identical pattern: same keys, same values, same key order. Patterns are compared by their JSON.stringify form, so { a: 1, b: 2 } and { b: 2, a: 1 } are different patterns, and { a: 1 } does not match { a: 1, b: 2 }.

When the same pattern is added twice, the first handler is kept.

API

new DevisPattern()

Creates a matcher. Each instance has its own patterns.

.add( {...pattern...}, handler )

Registers a pattern and the handler returned when an identical pattern is looked up. Returns the instance.

.find( {...pattern...} )

Returns the handler registered for this pattern, or null.

.call( {...pattern...}, [{...arguments...}], callback )

Calls the handler registered for this pattern with (arguments, callback). arguments defaults to {}. Does nothing when no handler matches.

.list( )

Returns the registered patterns as a JSON array string.

Upgrading from 1.x

• The native addon is gone, so installing no longer needs CMake or a C++ toolchain.
• Instances no longer share a single pattern table. In 1.x, two instances could resolve each other's patterns to the wrong handler.
• Node.js 22 or later is required.

License

MIT