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/**
* @callback EventCallback
* @param {string | Error | null} context
* @returns {void}
*/
/**
* @callback EventHandler
* @param {Event} event
* @returns {void}
*/
/**
* A function that creates an event handler for the `error` event.
* @param {EventCallback} callback A function called to handle the error context.
* @returns {EventHandler} A handler for the `error` event.
*/
function createErrorHandler(callback) {
return function errorHandler(event) {
if (!event || !event.error) {
return callback(null);
}
if (event.error instanceof Error) {
return callback(event.error);
}
// A non-error was thrown, we don't have a trace. :(
// Look in your browser's devtools for more information
return callback(new Error(event.error));
};
}
/**
* A function that creates an event handler for the `unhandledrejection` event.
* @param {EventCallback} callback A function called to handle the error context.
* @returns {EventHandler} A handler for the `unhandledrejection` event.
*/
function createRejectionHandler(callback) {
return function rejectionHandler(event) {
if (!event || !event.reason) {
return callback(new Error('Unknown'));
}
if (event.reason instanceof Error) {
return callback(event.reason);
}
// A non-error was rejected, we don't have a trace :(
// Look in your browser's devtools for more information
return callback(new Error(event.reason));
};
}
/**
* Creates a handler that registers an EventListener on window for a valid type
* and calls a callback when the event fires.
* @param {string} eventType A valid DOM event type.
* @param {function(EventCallback): EventHandler} createHandler A function that creates an event handler.
* @returns {register} A function that registers the EventListener given a callback.
*/
function createWindowEventHandler(eventType, createHandler) {
/**
* @type {EventHandler | null} A cached event handler function.
*/
let eventHandler = null;
/**
* Unregisters an EventListener if it has been registered.
* @returns {void}
*/
function unregister() {
if (eventHandler === null) {
return;
}
window.removeEventListener(eventType, eventHandler);
eventHandler = null;
}
/**
* Registers an EventListener if it hasn't been registered.
* @param {EventCallback} callback A function called after the event handler to handle its context.
* @returns {unregister | void} A function to unregister the registered EventListener if registration is performed.
*/
function register(callback) {
if (eventHandler !== null) {
return;
}
eventHandler = createHandler(callback);
window.addEventListener(eventType, eventHandler);
return unregister;
}
return register;
}
const handleError = createWindowEventHandler('error', createErrorHandler);
const handleUnhandledRejection = createWindowEventHandler(
'unhandledrejection',
createRejectionHandler
);
module.exports = {
handleError: handleError,
handleUnhandledRejection: handleUnhandledRejection,
};
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