Try catch block is not catching nested callbacks

Question

I'm trying to understand how to use try/catch when it comes to nested callbacks. Why doesn't this piece of code catch my new error ?

function test(cb) {
  setTimeout(function() {
    throw new Error("timeout Error");
  }, 2000);
}

try {
  test(function(e) {
    console.log(e);
  });
} catch (e) {
  console.log(e);
}

Answer 1

The error happens asynchronously, when the function passed to setTimeout runs. By the time the error is thrown, the test function has already finished executing.

Answer 2

There are many ways to set a timer for Javascript execution. Here's one way that uses Promise.race():

(async () => {
  try {
    await Promise.race([

      // Timer.
      new Promise((res, rej) => {
        setTimeout(() => {
          rej("Timeout error!");
        }, 2000);
      }),

      // Code being timed.
      new Promise((res, rej) => {
        // Do some stuff here.
        // If it takes longer than 2 seconds it will fail.
        res("Finished in under 2 seconds.");
      })

    ]);
  } catch (err) {
    console.log("we got an err: " + err);
  }
})();