solcjs is available as an npm package with the name solc. You can install the solcjs npm package locally or globally just like any other npm package. If this package is installed globally, then solcjs, a command-line tool, will be available. So, in order to install the command-line tool, run this command:
npm install -g solc
Now go ahead and run this command to see how to compile solidity files using the command-line compiler:
solcjs -help
We won't be exploring the solcjs command-line tool; instead, we will learn about the solcjs APIs to compile solidity files.
By default, solcjs uses compiler version matching as its version. For example, if you install solcjs version 0.4.8, then it will use the 0.4.8 compiler version to compile by default. solcjs can be configured to use some other compiler versions too. At the time of writing this, the latest version of solcjs is 0.4.8.