Rails - Could not find a JavaScript runtime?


Question

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.

1
244
4/17/2013 1:45:44 PM

Accepted Answer

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
469
7/27/2014 2:22:40 AM

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+


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