Callbackhell.com Website Review

that uses callbacks, is hard to get right intuitively. A lot of code ends up looking like this: fs.readdir(source, function (err, files) { if (err) { console.log('Error finding files: ' + err) } else { files.forEach(function (filename, fileIndex) { console.log(filename) gm(source + filename).size(function (err, values) { if (err) { console.log('Error identifying file size: ' + err) } else { write Ja*aScript in a way where execution happens visually from top to bottom. Lots of people make this mistake! In other languages like C, Ruby or Python there is the expectation that whatever happens on line 1 will finish before the code on line 2 starts running and so on down the file. As you will learn, Ja*aScript is different. ## What are callbacks? Callbacks are just the name of a convention for using Ja*aScript functions. There isn't a special thing called a 'callback' in the Ja*aScript language, it's just a convention. Instead of immediately returning some result like most functions, functions that use callbacks take some time to produce a result. The word 'asynchronous', aka 'async' just means 'takes some time' or 'happens in the future, not right now'. Usually callbacks are only used when In this case the gif might take a very long time to do*nload, and you don't want your program to pause (aka 'block') while waiting for the do*nload to finish. Instead, you store the code that should run after the do*nload is complete in a function. This is the callback! You give it to the `do*nloadPhoto` function and it will run your callback (e.g. 'call you back later') when the do*nload is complete, and pas* in the handlePhoto (error, photo) { if (error) console.error('Do*nload error!', error) else console.log('Do*nload finished', photo) } console.log('Do*nload started') The biggest hurdle people have when trying to understand callbacks is understanding the order that things execute as a program runs. In this example three major things happen. First the `handlePhoto` function is declared, then the `do*nloadPhoto`