Intro to Docable Notebooks

Docable Notebooks provide a way for viewing normal markdown files in an interactive and executable format. To enable this, you simply need to add some annotations to your document. For example, let’s see a simple example markdown for making a command cell that can be executed in Docable:

This is a docable cell which represents a command:

```bash|{type:'command'}
date
```

Docable notebooks will turn the markdown above into an interactive and executable document. To execute the cell, simply hover your mouse over the cell and press the play button:

This is a docable cell which represents a command:

[command:]

date

Now suppose you wrote a tutorial in markdown, this is how it would look like:

Basic Logging in Node.JS

If you’ve ever written code in JavaScript before, console.log() is most likely one of the first things you learned to use. console also provides many other methods which can be useful for basic logging of different events in you code. In this notebook, we’re going to see another method, console.error(), which can be useful for logging errors.

Let’s write a simple script (./log.js) to better understand these methods:

[file:]

log.js

console.log('this is a log message in stdout\n');
console.error('this is a log message in stderr\n');

Now if we simply run this script, it may look like console.log() and console.error() are doing the exact same thing:

[command:]

node log.js

So what makes these two methods different?

The main difference is the stream in which they write to. console.log() prints to stdout while console.error() prints to stderr. When we run something in terminal, we see a stream of both stdout and stderr without any visual indication for differentiating between the two. However, we can redirect these two streams to be written in separate files:

[command:]

node log.js > /tmp/stdout 2> /tmp/stderr

Now if we inspect /tmp/stdout we can see what part of ./log.js output was written in stdout stream:

[command:]

cat /tmp/stdout

We can see this is what console.log('this is a log message in stdout'); printed.

Similarly, if we inspect /tmp/stderr we can see what was printed to stderr stream:

[command:]

cat /tmp/stderr

And we can see this is what console.error('this is a log message in stderr'); printed.

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