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function doSomeAsyncHTTPRequest(callback) {

  setTimeout(callback, 2000);

}

​

console.log('first log')

​

// lets send some http-request

doSomeAsyncHTTPRequest((result) => {

  // The function that made the request executed this callback here when the request finished

  console.log('third log');

});

​

// the code immediately continues executing. It doesn't wait for the request to finish.

// Thats why we call it asynchronous

console.log('second log');