ObserverJs

ObserverJs is a lightweight JavaScript library that provides a simple and intuitive way to manage and execute event callbacks. It allows you to register event callbacks, execute them with before and after hooks, and trigger them together.

Installation

npm install @nightmaregaurav/observer.js

Usage

import { EventScope } from '@nightmaregaurav/observer.js';

// Create an instance of EventScope
const eventScope = new EventScope();

// Register event callbacks
const eventId = eventScope.register(callback);

// Add before, after, and together callbacks
eventScope
    .before(eventId, beforeCallback)
    .after(eventId, afterCallback)
    .together(eventId, togetherCallback);

// Trigger the event
eventScope.trigger(eventId, ...params).then(result => {
    // Handle the result
});

Example

function studentLeave(uid: number) {
    console.log("Student", uid, "Left");
}

function teacherLeave(uid: number) {
    console.log("Teacher", uid, "Left");
}

const eventScope = new EventScope();

const studentLeaveEventId = eventScope.register(studentLeave);
const teacherLeaveEventId = eventScope.register(teacherLeave);

eventScope
    .before(studentLeaveEventId, (eventId, eventParams) => console.log("Open The Door"))
    .after(studentLeaveEventId, (eventId, eventParams, hasErrors) => console.log("Close The Door"))
    .before(teacherLeaveEventId, (eventId, eventParams) => console.log("Open The Door"))
    .together(teacherLeaveEventId, (eventId, eventParams) => console.log("Students thank teacher"))
    .after(teacherLeaveEventId, (eventId, eventParams, hasErrors) => console.log("Close The Door"));


const studentLeaveExecutor = eventScope.getExecutor(studentLeaveEventId);
if (studentLeaveExecutor) studentLeaveExecutor(1).then();
// above 2 lines are same as
eventScope.trigger(studentLeaveEventId, 1).then();

`
    >>> Open The Door
    >>> Student 1 Left
    >>> Close The Door
`

const teacherLeaveExecutor = eventScope.getExecutor(teacherLeaveEventId);
if (teacherLeaveExecutor) teacherLeaveExecutor(2).then();
// above 2 lines are same as
eventScope.trigger(teacherLeaveEventId, 2).then();

`
    >>> Open The Door
    >>> Teacher 2 Left  // or "Students thank teacher"
    >>> Students thank teacher  // or "Teacher 2 Left"
    >>> Close The Door
`

import { EventScope } from 'observer-js';

function onLeave(name) {
    console.log(name, "left");
}

const eventScope = new EventScope();

const leaveEventId = eventScope.register(onLeave);

eventScope
    .before(leaveEventId, () => console.log("Opening the door"))
    .after(leaveEventId, () => console.log("Closing the door"));

const leaveExecutor = eventScope.getExecutor(leaveEventId);
if (leaveExecutor) {
    leaveExecutor("Alice").then(() => {
        console.log("Event executed successfully");
    });
}

License

ObserverJs is released under the MIT License. You can find the full license details in the LICENSE file.

Made with ❤️ by NightmareGaurav.

Open For Contribution

We welcome contributions from the community! If you have any improvements, bug fixes, or new features to add, please feel free to fork this repository and submit a pull request. We appreciate your contributions!