Printing function name and arguments in Node.js with debug

Question

I'd like to use debug to be able to print method / function names and arguments on every call.

What's the best way to achieve this instead of placing customized debug statements in every function like this:

async function getFilePaths(path, id) {
  debug(`async function getFilePaths(path = ${path}, id = ${id})`);
  // ...
}

When writing an object to debug in Chrome it allows to view all it's properties — Amir Geri
– Amir Geri, Commented Jul 16, 2015 at 5:21
If you want to know where you are at a certain step, you can do console.trace(), though I only recommend using it in the console window. I haven't tested with IE10+, but console.trace() and console.debug() broke IE 9 unless the developer window was open. — ps2goat
– ps2goat, Commented Jul 16, 2015 at 5:23
now that I see it's node.js, my comment is probably not related. — ps2goat
– ps2goat, Commented Jul 16, 2015 at 5:23

Preston Van Loon · Accepted Answer · 2015-07-16 05:34:43Z

1

You could do something like this:

function logDebug(fn, args) {
   debug(fn.name + args.toString());
}

And call it in your function

function getFilePaths(path, id) {
  logDebug(getFilePaths, arguments);
}

Note: Function.name is a new technology supported in ES6.

answered Jul 16, 2015 at 5:34

Preston Van Loon

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3 Comments

krl Over a year ago

This is closer to what I want. arguments.toString() doesn't play well with debug, so it should be Array.slice(arguments). However I still need to specify function name explicitly. Something I'd like to avoid.

Preston Van Loon Over a year ago

You should not slice on arguments because it prevents optimizations in JavaScript engines (V8 for example). Instead, try constructing a new array by iterating through the arguments object. And you could try function.caller but it's not supported widely. developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

krl Over a year ago

This is for debugging purposes, so I'm not concerned about performance. Using debug alone slows the whole thing down quite a lot.

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