console: warn() static method

Note: This feature is available in Web Workers.

The console.warn() static method outputs a warning message to the console at the "warning" log level. The message is only displayed to the user if the console is configured to display warning output. In most cases, the log level is configured within the console UI. The message may receive special formatting, such as yellow colors and a warning icon.


warn(val1, /* …, */ valN)
warn(msg, subst1, /* …, */ substN)



A list of JavaScript values to output. A representation of each of these values is output to the console in the order given with some type of separation between each of them. There is a special case if obj1 is a string, which is described subsequently.


A JavaScript string containing zero or more substitution strings, which are replaced with subst1 through substN in consecutive order up to the number of substitution strings. See Using string substitutions for a description of how substitutions work.


JavaScript values with which to replace substitution strings within msg. If there are more substutition values than there are substitution strings, the extra values are themselves written to the console after the detailed assertion message in the same manner as when there's no format string.

See Outputting text to the console in the documentation of console for further details.

Return value

None (undefined).


Console Standard
# warn

Browser compatibility

BCD tables only load in the browser

See also