Node.js, MongoDB, and AngularJS Web Development

Asynchronous File Reading

The asynchronous method of file reading puts the read request on the event queue and then returns control back to the calling code. The actual read does not take place until the event loop picks up the read request and executes it. You need to be careful when performing multiple asynchronous read requests on the same file because you cannot guarantee their execution order unless you wait for the first read callback to execute before executing the next read. Typically the simplest way to do this is to nest reads inside the callback from the previous read. The code in Listing 6.7 illustrates this process.

To read from a file asynchronously, first open it by using open() and then after the callback from the open request ...