Node.js Module Resolution by visual example

Node.js has a very clever design for module path resolution and code loading. Most languages punt when asked to load two modules depending on different versions of a shared third module, but not Node. This presentation depicts a handful of module loading scenarios by demonstrating the filesystem layout for each.

Transcript

1. @kunklejr Node.js Module Resolution Jeff Kunkle April 19, 2012
2. Path Resolution
3. require(“./mymodule.js”); 1
4. mymodule.js /projects/preso/ main.js require(“./mymodule.js”);
5. require(“./mymodule”); 2
6. /projects/preso/ main.js require(“./mymodule”);
7. mymodule.js /projects/preso/ main.js require(“./mymodule”);
8. mymodule.js /projects/preso/ mymodule.json main.js require(“./mymodule”);
9. mymodule.js /projects/preso/ mymodule.json mymodule.node main.js require(“./mymodule”);
10. require(“./mymodule”); /projects/preso/ main.js mymodule/ package.json init.js
11. require(“./mymodule”); mymodule/ /projects/preso/ index.js main.js
12. require(“./mymodule”); mymodule/ /projects/preso/ index.node main.js
13. require(“mymodule”); 3
14. require(“mymodule”); node_modules/ /usr/local/node/lib/ index.js mymodule/ * assuming mymodule was a core Node.js module
15. require(“mymodule”); node_modules/ /projects/preso/ index.js main.js mymodule/
16. require(“mymodule”); node_modules/ /projects/ index.js main.js mymodule/ preso/
17. require(“mymodule”); node_modules/ / index.js main.js mymodule/ projects/ preso/
18. require(“mymodule”); Global load paths also exist, but don’t use them.
20. Dependency Resolution Magic!
21. A B C v1.0 v2.0
22. a/ node_modules/ c/ b/ node_modules/ c/ b.js a.js c.js c.js ./node_modules/ v1.0 v2.0
23. a/ b/ b.js a.js ./node_modules/ c/ c.js
24. Jeff Kunkle @kunklejr