Console.log bug?

[dtroydev]

• Version: v10.6.0
• Platform: Mac OS 10.13.6
• Subsystem: console

Suppose we used console.log as follows:

console.log('I\'m trying to escape', false);
console.log(false, 'I\'m trying to escape');

This will then output the following:

I'm trying to escape false
false 'I\'m trying to escape'

As can be seen the backslash is treated differently between lines.

Also in the actual shell, the colouring is not present in the first line, but is present in the second line.
(boolean is yellow and string is green)

Is this by design or a bug?

[addaleax]

Is this by design or a bug?

I agree that it’s super confusing, but it’s by design. If the first argument is a string, it is used as a format string – the console.log() documentation isn’t great on explaining this, but it links to util.format(). There, we find this sentence:

the first argument is not a string then util.format() returns a string that is the concatenation of all arguments separated by spaces. Each argument is converted to a string using util.inspect().

I really think we should improve the console.log documentation here, though.

[addaleax]

I’m reopening this so that we can keep it as a todo for the documentation, hope that’s okay.

[lovinglyy]

I would love to do this one as good first issue, I do have a contribution already but not that relevant, is it okay?

[lundibundi]

@lovinglyy Yes, go on. 👍

If you have any questions you can post them here.

[silverwind]

I think our behaviour might not be conforming the Console Standard. If I interpret the spec correctly, we should arrive here with logLevel being 'log' and there is no mentioning that the first argument is to be treated differently from the others, or am I missing something?

[devsnek]

@silverwind it uses https://console.spec.whatwg.org/#formatter

[silverwind]

@devsnek I don't think so. It should branch to Printer on step 5 of Logger when the first argument does not contain a format specifier (e.g. %d):

If first does not contain any format specifiers, perform Printer(logLevel, args).

[lovinglyy]

Should I wait to see if there will be changes in console.log behavior before doing pull requests to the docs?