How to Print Function Signature in javascript

Question

I have a function:

fs.readFile = function(filename, callback) {     // implementation code. }; 

Sometime later I want to see the signature of the function during debugging.

When I tried console.log(fs.readFile) I get [ FUNCTION ].

That does not give me any information.

How can I get the signature of the function?

Answer 1

In node.js specifically, you have to convert the function to string before logging:

$ node > foo = function(bar, baz) { /* codez */ } [Function] > console.log(foo) [Function] undefined > console.log(foo.toString()) function (bar, baz) { /* codez */ } undefined >  

or use a shortcut like foo+""

Answer 2

If what you mean by "function signature" is how many arguments it has defined, you can use:

function fn (one) {} console.log(fn.length); // 1 

All functions get a length property automatically.