require(X) from module at path Y

. If X is a core module,

   a. return the core module

   b. STOP

. If X begins with './' or '/' or '../'

   a. LOAD_AS_FILE(Y + X)

   b. LOAD_AS_DIRECTORY(Y + X)

. LOAD_NODE_MODULES(X, dirname(Y))

. THROW "not found"

LOAD_AS_FILE(X)

. If X is a file, load X as JavaScript text.  STOP

. If X.js is a file, load X.js as JavaScript text.  STOP

. If X.json is a file, parse X.json to a JavaScript Object.  STOP

. If X.node is a file, load X.node as binary addon.  STOP

LOAD_AS_DIRECTORY(X)

. If X/package.json is a file,

   a. Parse X/package.json, and look for "main" field.

   b. let M = X + (json main field)

   c. LOAD_AS_FILE(M)

. If X/index.js is a file, load X/index.js as JavaScript text.  STOP

. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP

. If X/index.node is a file, load X/index.node as binary addon.  STOP

LOAD_NODE_MODULES(X, START)

. let DIRS=NODE_MODULES_PATHS(START)

. for each DIR in DIRS:

   a. LOAD_AS_FILE(DIR/X)

   b. LOAD_AS_DIRECTORY(DIR/X)

NODE_MODULES_PATHS(START)

. let PARTS = path split(START)

. let I = count of PARTS -

. let DIRS = []

. while I >= ,

   a. if PARTS[I] = "node_modules" CONTINUE

   b. DIR = path join(PARTS[ .. I] + "node_modules")

   c. DIRS = DIRS + DIR

   d. let I = I -

. return DIRS