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console.log and util.format formatting specifiers #10292
Description
The Chromium console supports format specifiers: https://developers.google.com/web/tools/chrome-devtools/console/console-write#string_substitution_and_formatting
In particular, both %i and %d specify an integral argument. Node.js does not perform the conversion for %i:
/* node.js */
> console.log("%i", 1234)
%i 1234
/* google chrome */
> console.log("%i", 1234)
1234
I think the fix is really simple: the relevant code is at https://github.com/nodejs/node/blob/master/lib/util.js#L86-L117 . Just adding the i case should be enough:
switch (f.charCodeAt(i + 1)) {
case 105: // 'i' <-- this is the new line, and it should appear just before the `d` case to make the fall through work
case 100: // 'd'
If it makes sense I can send a PR
Activity
silverwind commentedon Dec 15, 2016
Not sure if aliasing
%ito the current%dis a good idea. In all browsers that I've tested, those two convert to integer (while providing%fas a means to format floats). In node,%dserves a double purpose of supporting both float and integer.%fbehaviour is inconsistent between browsers. Forconsole.log('%f', 1.5)Safari and Firefox print'1.500000'while Chrome does'1.5'.I'd propose the following steps to fix:
%dconvert to integer and alias%ito it. This would be a breaking change.%fwith once we're clear what to do about the0padding.Fishrock123 commentedon Dec 15, 2016
As mentioned in #1716 (comment) we don't implement the
console"spec" and honestly I don't think we are really about to. :/We could do
%fif it's reasonable I guess, honestly don't see much reason to not support%iin whatever way we think it should work either.jsinmotion commentedon Dec 15, 2016
I agree that there is no point in chasing a "spec" that doesn't exist, but this is a case where the major browser vendors agree!
As of 2016 Dec 15 this is the current conversion specifier support:
IMHO nodejs should support %d %i %s %f
%oin the same way that other browsers support the feature. The others, like IE's %x for hex, probably aren't critical.This table is based on the following browser vendor resources:
Chrome: https://developers.google.com/web/tools/chrome-devtools/console/console-write#string_substitution_and_formatting
IE: https://msdn.microsoft.com/en-us/library/hh696634.aspx#Anchor_4
Firefox: https://developer.mozilla.org/en-US/docs/Web/API/Console#Using_string_substitutions
EDIT: originally supported following browsers use of
%obut that would be confusing since printf uses%ofor octal integers.Fishrock123 commentedon Dec 16, 2016
Well, there is definitely a "spec" but it's not really official to the language by any means: https://github.com/DeveloperToolsWG/console-object/
jsinmotion commentedon Dec 16, 2016
The browsers actually do something wholly unexpected with the string conversions:
My expectation is that "%s" would use the appropriate toString method, so that the output would be "foo". nodejs actually does what I would expect. Oddly, Chrome and Safari print "Object" rather than calling the object's toString.
Since I think node is actually doing the right thing here, I will close now and try to bring this discussion to the relevant browser vendors before revisiting in node
silverwind commentedon Dec 16, 2016
Let's leave this open, there's certainly room for improvement on our side, and I like you nice table :)
jsinmotion commentedon Dec 16, 2016
@silverwind The confounding factor related to the trailing digits in the floating format is support for the printf width and precision fields. Firefox has limited support but Chrome completely ignores those fields. If you want to see a difference in FF, try
console.log('%.1f', 1.5)-- that should print 1.5 in FF. If I had to guess, chrome's behavior for %f is closest to the POSIX%.17g.Since there are NPM modules like printj that fully replicate the POSIX printf spec, it seems fair to argue that node core should only support basic substitutions and people should fall back to userland code for heavy lifting.
@robertkowalski @terinjokes since you are mentioned in the whatwg spec, maybe you can chime in.
24 remaining items
Trott commentedon Jan 11, 2017
@silverwind The
ctc-agendahas been removed. If you think this needs a decision from the CTC (and I'm guessing you do, but I don't know for sure), you may want to add it back and say so.util: change %d to format a integer, add %i and %f
util: add %i and %f formatting specifiers
silverwind commentedon Mar 29, 2017
%iand%fhave been added.%dstill formats as Number which is incompatible with browsers for floats, but there were concerns about backward compatibilty on that one.%olooks like a candidate we could possibly support too, reopening for this purpose.[-]console.log and util.format should support the %i integer conversion[/-][+]console.log and util.format formatting specifiers[/+]util: add %i and %f formatting specifiers
Trott commentedon Jul 30, 2017
I'm going to close this and open a separate issue for
%o.Trott commentedon Jul 30, 2017
#14545
util: add %i and %f formatting specifiers