Installing it with npm gets you a command-line tool that can be used to analsyse multiple paths. You could also use it as part of a project's build process, perhaps during a linting phase. I ran it on the source to Ghost, and it found matches in the server code between password reset and invitations, which makes sense. The command I used was jsinspect -t 30 -i core/server.
This project is based on the Acorn ECMAScript parser. Acorn is used to generate lists of nodes that are compared based on a similarity threshold (set by -t).
You have the freedom to specify a threshold determining the smallest subset of nodes to analyze. This will identify code with a similar structure, based on the AST node types, e.g. BlockStatement, VariableDeclaration, ObjectExpression, etc. For copy-paste oriented detection, you can even limit the search to nodes with matching identifiers.
For bonus points, you can try combining jsinspect with a script that searches for the copied code on Stack Overflow!