The symbol-observable package is primarily used to polyfill the Observable symbol, which is a proposed addition to the ECMAScript standard. It allows JavaScript objects to be observable, meaning that other objects can subscribe to them and react to changes. This is particularly useful in reactive programming models and libraries, such as RxJS, where data streams and their transformations are a core concept.

What are symbol-observable's main functionalities?

Polyfill for Observable Symbol

This code demonstrates how to use the symbol-observable package to make an object observable. It defines a simple observable that emits 'hi' every second. An observer subscribes to this observable to log the emitted values. This showcases how symbol-observable can be used to implement the observer pattern in JavaScript.

"use strict";

const symbolObservable = require('symbol-observable').default;

console.log(typeof symbolObservable); // 'symbol' in environments with native Symbol support

const obj = {};
obj[symbolObservable] = function () {
  return {
    subscribe(observer) {
      const intervalID = setInterval(() => observer.next('hi'), 1000);

      return {
        unsubscribe() {
          clearInterval(intervalID);
        }
      };
    }
  };
};

const observable = obj[symbolObservable]();
const subscription = observable.subscribe({
  next(val) { console.log(val); },
  complete() { console.log('Done'); }
});

// Later:
// subscription.unsubscribe();

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