why use sync functions node.js

Question

Everyone recommends using async (non-blocking) functions instead of sync functions in Node.js .

So whats the use of sync functions in node.js if they are not recommended?

For example : Why use fs.readFileSync() if fs.readFile() can do the same job without blocking?

Answer 1

Sync functions are useful, especially on startup, where you want to make sure that you have the result prior to executing any more code.

For example, you could load in a configuration file synchronously. However, if you are trying to do a file read during a live request, you should use async functions so you don't block other user requests.

Answer 2

Sometimes you want to execute code once you have finished reading or writing to a file. For example

function () {
    array.forEach(function(data) {
        fs.writeFile(data)
    });

    // do this after forEach has finished looping, not after files have finished being writen to
}

As apposed to:

function () {
    array.forEach(function(data) {
        fs.writeFileSync(data)
    });

    // do this after all files have been written to
}