from the article: Creating a Steam Trade Bot with Node.js. This was written in December of 2014 and utilizes node-steam 0.6.8.
If you're getting Undefined is not a function errors at client.logOn, you likely have a newer version of node-steam installed. Please refer to this comment for information on installing the correct version. A new article will be published shortly with node-steam v1.0 in mind.