Custom console.log function that tells you the line that it was invoked

Question

Here's a simple console.log function that outputs stuff to the console:

function u(x) { console.log(x); } // line 41

But this is not altogether efficient for debugging purposes, as the browser will always output the line that console.log() was invoked on, which is line 41 in this case.

The error or whatever could be on line 741, but it would not matter. I realize that I could simply use console.log all the time instead of creating a shorter custom function, but if I don't have to, well...

How could u(x) display the actual line that it was invoked on?

Cheers!

Do you definitely want to do with WITHOUT sending the line number to the function or are you happy to send the line number? — Popnoodles, Feb 17 '14 at 22:52
xbrowser solution here https://github.com/stacktracejs/stacktrace.js — Popnoodles, Feb 17 '14 at 22:57
well, I could certainly use the option of sending the line number...Thanks for the links! — lexica98, Feb 17 '14 at 22:59

score 1 · Answer 1 · edited May 23 '17 at 12:10

1

You are asking a difficult question because I have to get in to handling exceptions and what is the correct way to do that. Typically in languages like Java, you pass around exceptions instead of error messages. You could do something like

u(new Error("this is my error"))

in function(e) you could do console.log(e) where that prints the correct stack of the current execution.

Look at How to get JavaScript caller function line number? How to get JavaScript caller source URL? on how to get the actual line number.

Hope this helps.

edited May 23 '17 at 12:10

Community

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1

answered Feb 17 '14 at 22:48

Amir Raminfar

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"in function(e)".. what function(e)? – Popnoodles Feb 17 '14 at 23:02
`function u(exception) {...}`. It is much cleaner to pass around the error than passing the message and line number. – Amir Raminfar Feb 17 '14 at 23:08

score 1 · Accepted Answer · answered Feb 17 '14 at 22:54

It's very simple to send the line number to the function. I'm not sure it's so simple to trace without a larger solution.

function u(x, l){
    console.log(x + ' on line ' + l);
}

u('test', new Error().lineNumber)

EDIT: However, I've learned this only works in FF and Opera. There is a cross-browser solution here https://github.com/stacktracejs/stacktrace.js

score 0 · Answer 3 · answered Feb 17 '14 at 22:52

0

In at least chrome you can call console.trace() to log a stack trace to the console.

Edit:

function u(x) {
    console.log(x);
    console.trace();
}

Should give you what you want.

answered Feb 17 '14 at 22:52

Ben

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I assumed he would realize to put it into his custom function, but I can edit it in. – Ben Feb 17 '14 at 22:54
Nice! Looks like I'll have to go cross-browser for full support, although it's really irrelevant to the user, just use chrome or firefox for development lol. – lexica98 Feb 17 '14 at 22:56
Firefox supports console.trace() too (at least my edition of it). – lexica98 Feb 17 '14 at 23:05

Custom console.log function that tells you the line that it was invoked

3 Answers3