UnhandledPromiseRejectionWarning originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). A rejected promise is like an exception that bubbles up towards the application entry point and causes the root error handler to produce that output. It usually happens in async await functions, and there’s an easy fix.
const functionName = async (arguments) => {
try {
// Your code here
} catch (error) {
// Handle rejection here
}
};
A nice way to wait for several Promises to resolve to use the Promise.all function. It expects an Array of Promises, and produces a Promise that resolves to an Array containing the values that the individual Promises resolved to. Furthermore, it only resolves after the last Promise resolves. If any of its input Promises rejects, then the entire Promise.all expression rejects as well. It effectively “runs” all of its input processes “at the same time”, emulating the classic “fork-join” pattern.