A 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.

npm install devisPattern

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' }
});

find 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.

match is the partial lookup used by Devis 4.1: a registered pattern matches when all its keys appear in the looked-up pattern with the same values. The pattern with the most keys wins, and the first registered wins a tie:

devisPattern.add({ role: "math" }, any);
devisPattern.add({ role: "math", cmd: "sum" }, sum);

devisPattern.match({ role: "math", cmd: "sum", version: 2 }); // { handle: sum, size: 2 }
devisPattern.match({ role: "math", cmd: "divide" });          // { handle: any, size: 1 }
devisPattern.match({ cmd: "sum" });                           // null

Creates a matcher. Each instance has its own patterns.

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

Returns the handler registered for this pattern, or null.

Returns { handle, size } for the most specific registered pattern contained in this one, where size is its number of keys, or null.

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

Returns the registered patterns as a JSON array string.

• 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.

MIT