Noah's Javascript Debugging tools
These are just three functions that help me debug Javascript code, which I found myself re-implementing over and over. Now I add them to my devDependencies. I don't pretend these are useful for anyone else, they're just what I like.
taplog(label, x) prints the label and x, then returns x. Useful when you want to log a value nested in.
trace(fn) transforms a function to print its name, the arguments it received, and its return value, before returning.
trace(name, fn) is like trace except you provide a function name. (Useful for unnamed functions.)
repr(x) returns a string representation of x. For arrays, this is [n], where n is the length of the array. For objects, this is a list of keys in braces, like {foo, bar, baz}.