rc-hooks/es/utils/windowVisible.js

React Hooks Library.

// from swr
import { isDocumentVisible } from './index';
var listeners = [];
function subscribe(listener) {
    listeners.push(listener);
    return function unsubscribe() {
        var index = listeners.indexOf(listener);
        listeners.splice(index, 1);
    };
}
var eventsBinded = false;
if (typeof window !== 'undefined' && window.addEventListener && !eventsBinded) {
    var revalidate = function () {
        if (!isDocumentVisible())
            return;
        for (var i = 0; i < listeners.length; i++) {
            var listener = listeners[i];
            listener();
        }
    };
    window.addEventListener('visibilitychange', revalidate, false);
    // only bind the events once
    eventsBinded = true;
}
export default subscribe;