Rails – Could not find a JavaScript runtime?

Rails – Could not find a JavaScript runtime?

I created a new Rails project using rails 3.1.0.rc4 on my local machine but when I try to start the server I get:
Could not find a JavaScript runtime. See here for a list of available runtimes. (ExecJS::RuntimeUnavailable)
Note: This is not about Heroku.


Solution 1:

Installing a javascript runtime library such as nodejs solves this

To install nodejs on ubuntu, you can type the following command in the terminal:

sudo apt-get install nodejs

To install nodejs on systems using yum, type the following in the terminal:

yum -y install nodejs

Solution 2:

Note from Michael 12/28/2011 – I have changed my accept from this (rubytheracer) to above (nodejs) as therubyracer has code size issues. Heroku now strongly discourage it. It will ‘work’ but may have size/performance issues.

If you add a runtime, such as therubyracer to your Gemfile and run bundle then try and start the server it should work.

gem 'therubyracer'

A javascript runtime is required for compiling coffeescript and also for uglifier.

Update, 12/12/2011: Some folks found issues with rubytheracer (I think it was mostly code size). They found execjs (or nodejs) worked just as well (if not better) and were much smaller.

n.b. Coffeescript became a standard for 3.1+

Solution 3:

Add following gems in your gem file

gem 'therubyracer'
gem 'execjs'

and run

bundle install


Install Node.js to fix it permanently for all projects.

Solution 4:

sudo apt-get install nodejs does not work for me. In order to get it to work, I have to do the following:

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:chris-lea/node.js
sudo apt-get update
sudo apt-get install nodejs

Hope this will help someone having the same problem as me.

Solution 5:

On the windows platform, I met that problem too
The solution for me is just add


to the PATH

and restart the computer.

Solution 6:

I had this issue on a Windows machine and installing node.js was the solution that finally worked for me. This came after trying multiple other routes including trying to get ‘therubyracer’ working. Though the github for node.js suggests that installation on windows is still unstable, the website at http://nodejs.org/ had a Windows installer which worked perfectly.