Getting Started

Installation

npm install meos.js

Initialising the WASM module

Every MEOS.js program must call initMeos() once before using any type. The function loads and compiles the WebAssembly binary and is asynchronous.

import { initMeos, IntSpan } from 'meos.js';

await initMeos();

const s = IntSpan.fromBounds(1, 10);
console.log(s.lower()); // 1
console.log(s.upper()); // 10
s.free();

initMeos() is safe to call multiple times; subsequent calls return the cached module.

Memory management

MEOS.js objects wrap pointers to C-allocated memory on the WASM heap. You are responsible for releasing that memory when you are done.

Manual release: call .free():

const span = IntSpan.fromBounds(1, 10);
// ... use span ...
span.free();

Automatic release: use the using declaration (TypeScript 5.2+, ES2022 target):

using span = IntSpan.fromBounds(1, 10);
// span.free() is called automatically at the end of the block

Operations that create new objects (e.g. copy(), union(), intersection()) also allocate new WASM memory, free those results too.

What is MEOS?

MEOS (Mobility Engine Open Source) is the C library at the core of MobilityDB. It provides temporal types (types that track how a value changes over time) together with the span, span-set, and set primitives needed to represent ranges of numbers, dates, and timestamps.

MEOS.js compiles MEOS to WebAssembly and exposes its types as idiomatic TypeScript classes.