This has been renamed to batchfile.
Node.js - batchtransform
Batch transform/convert a collection of files e.g. convert a collection of markdown template files to html files.
Why?
Writing logic to
- iterate through files
- check that files exist
- read the file
- convert file
- check that destination directory exists
- if not, make the directory
- write the file
- be notified when all of the files are done
sucks.
Scenario
Let's assume that we have a collection of Markdown files with [Mustache][mustache] templates. We want to create HTML files from these Markdown files.
Let's assume that our Markdown looks like this:
My Biography
============
By {{author}}
-------------
... some text ...
Old-School Way
var marked = require('marked')
, hogan = require('hogan.js')
, fs = require('fs')
, path = require('path')
, mkdirp = require('mkdirp');
var files = ['bio1.md', 'bio2.md', 'bio3.md'];
var authors = ['JP', 'Leslie', 'Chris'];
var pending = files.length;
files.forEach(function(file, i) {
fs.exists(file, function(itDoes) {
it (!itDoes) {
throw new Error(file + " does not exist.");
} else {
fs.readFile(file, 'utf8', function(err, data) {
if (err) {
throw err;
} else {
var bn = path.basename(file, '.md');
var newMd = hogan.compile(data).render({author: authors[i]});
var html = marked(newMd);
var newFile = path.join('/tmp/output/', bn + '.html');
var dir = path.dirname(newFile);
fs.exists(dir, function(dirExists) {
function wf(err) {
if (err) {
throw err;
}
fs.writeFile(newFile, html, function(err) {
if (err) {
throw err;
} else {
pending -= 1;
if (pending === 0) {
console.log("Phew, we are done!");
}
}
})
}
if (!dirExists) {
mkdirp(dir, wf);
} else {
wf(null);
}
})
}
})
}
})
});
Yuck. Very long and hard to follow code. Yes, you can definitely simplify this by using libraries such as async, seq, or batchflow. batchtransform
itself uses batchflow.
Let's see the previous sample rewritten using batchtransform
.
New-School way
var marked = require('marked')
, hogan = require('hogan.js')
, btf = require('batchtransform');
var files = ['bio1.md', 'bio2.md', 'bio3.md'];
var authors = ['JP', 'Leslie', 'Chris'];
btf(files).transform(function(i, file, data, write) {
var bn = path.basename(file, '.md');
var newMd = hogan.compile(data.toString()).render({author: authors[i]});
var html = marked(newMd);
var newFile = path.join('/tmp/output/', bn + '.html');
write(newFile, html);
}).error(function(err) {
throw err;
}).end(function() {
console.log('We are done! Much clearer!');
});
Installation
npm install batchtransform
Methods
btf(files)
Constructor function.
files: can be either an array or strings
Returns new BatchTransform object.
Example:
var btf = require('batchtransform');
var myBatch = btf('f1', 'file2', 'readme.md');
transform(i, file, data, write)
Transformation callback.
i: index of current iteration
file: file path
data: data buffer (don't forget to convert to a string)
write: the write callback. Call this last, and call it only once.
error(callback)
The error callback.
end(callback)
The end callback.
Author
node-batchtransform
was written by JP Richardson. You should follow him on Twitter @jprichardson. Also read his coding blog Procbits. If you write software with others, you should checkout Gitpilot to make collaboration with Git simple.
License
(MIT License)
Copyright 2012, JP Richardson jprichardson@gmail.com