Thursday, June 6, 2013

My journey in discovering Grunt: A JavaScript Task Runner

Some weeks ago, I was looking at the html2canvas library on GitHub. I wanted to test the code so I decided to clone it to my local repository. However the source code is split over multiple files, so if you want to use it inside your application you have to build it first.
My first naïve attempt, was just running the grunt.js file as found in the project directory. This failed with the following message:
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Going back to the project site, I found that you have to use Grunt(a node.js plugin) for building:
The library uses grunt for building. Alternatively, you can download the latest build from here.
Run the full build process (including lint, qunit and webdriver tests):
$ grunt
Ok, let’s try this. I opened a command window and tried to execute the command(notice that I already have node.js installed on my machine):

npm install -g grunt-cli

This will put the grunt command in your system path, allowing it to be run from any directory.

Let’s now run the grunt command(you can use both grunt and grunt.cmd):

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Woops. No success. I figured out that I was using a more recent version of Grunt than the project was using. In the meanwhile the convention had changed and instead of having a grunt.js file in your project directory, you need to name it gruntfile.js(More info here: http://gruntjs.com/getting-started).

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The Gruntfile.js or Gruntfile.coffee file is a valid JavaScript or CoffeeScript file that belongs in the root directory of your project, next to the package.json file, and should be committed with your project source.

A Gruntfile is comprised of the following parts:
· The "wrapper" function
· Project and task configuration
· Loading grunt plugins and tasks
· Custom tasks
Run the command again, still failure:


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Grunt itself is doing nothing, it only loads a set of plugins and tasks and execute them. It seems that grunt tried to execute some tasks that I didn’t install. So let’s install the missing packages and try again:

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Ok, last attempt, this time we finally got Grunt working:

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And now I have a nice new tool in my toolbox.

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For a good introduction on Grunt, I can recommend reading http://www.elijahmanor.com/2013/04/angry-birds-of-javascript-mighty-eagle.html

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