SlimIO package to achieve Lazy evaluation on JavaScript Objects! It use getter/setter to evaluate a function which return the final value at runtime (only when the property is requested).

Requirements

• Node.js v12 or higher

Getting Started

This package is available in the Node Package Repository and can be easily installed with npm or yarn.

$ npm i @slimio/lazy
# or
$ yarn add @slimio/lazy

Usage example

// lp stand for Lazy Proxy
const lp = Lazy.of({});

lp.set("foo", () => "bar");
lp.set("hello", () => {
    // Do job here
});

module.exports = lp.value;

Under the hood the lib use the ECMAScript Reflection API to ensure that the property is set (else it will throw an Error).

const obj = Object.freeze({});
Lazy.defineProperty(obj, "foo", () => "bar"); // throw Error

API

defineProperty(target, propertyName, lazyFunctionValue): void

Define a new lazy property with a given name on target. Similar to Object.defineProperty.

The property descriptors will be defined as follow:

{
    "enumerable": true,
    "writable": false
}

lazy.of< T >(target: T): LazyClojure< T >

Create a lazy clojure described by the following interface:

interface LazyClojure<T> {
    set(propertyName: string, lazyFunctionValue: lazyHandler): void;
    value: T;
}

The set method is a mirror of the root defineProperty method.

const lp = Lazy.of({});
lp.set("foo", () => "bar");

const obj = lp.value;

Dependencies

License

MIT