Use the Console API to write messages to the Console from your JavaScript. See
Get Started With Logging Messages To The Console for an interactive introduction
to the topic. See Console Utilities API Reference if you're looking for the
convenience methods like debug(function) or monitorEvents(node) which are only available from
the Console.
console.assert(expression, object)
Log level: Error
Writes an error to the console when expression evaluates to false.
const x = 5;
const y = 3;
const reason = 'x is expected to be less than y';
console.assert(x < y, {x, y, reason});
console.assert() example above.
console.clear()
Clears the console.
console.clear();
If Preserve Log is enabled,
console.clear() is disabled.
See also: Clear the Console
console.count([label])
Log level: Info
Writes the number of times that count() has been invoked at the same
line and with the same label. Call console.countReset([label])
to reset the count.
console.count();
console.count('coffee');
console.count();
console.count();
console.count() example above.
console.countReset([label])
Resets a count.
console.countReset();
console.countReset('coffee');
console.debug(object [, object, ...])
Log level: Info
Identical to console.log(object [, object, ...]).
console.debug('debug');
console.debug() example above.
console.dir(object)
Log level: Info
Prints a JSON representation of the specified object.
console.dir(document.head);
console.dir() example above.
console.dirxml(node)
Log level: Info
Prints an XML representation of the descendants of node.
console.dirxml(document);
console.dirxml() example above.
console.error(object [, object, ...])
Log level: Error
Prints object to the Console, formats it as an error, and includes a stack trace.
console.error("I'm sorry, Dave. I'm afraid I can't do that.");
console.error() example above.
console.group(label)
Visually groups messages together until console.groupEnd(label) is called. Use
console.groupCollapsed(label) to collapse the group when it's
initially logged to the Console.
const label = 'Adolescent Irradiated Espionage Tortoises';
console.group(label);
console.info('Leo');
console.info('Mike');
console.info('Don');
console.info('Raph');
console.groupEnd(label);
console.group() example above.
console.groupCollapsed(label)
Same as console.group(label), except the group is initially collapsed when it's logged to the Console.
console.groupEnd(label)
Stops visually grouping messages. See console.group.
console.info(object [, object, ...])
Log level: Info
Identical to console.log(object [, object, ...]).
console.info('info');
console.info() example above.
console.log(object [, object, ...])
Log level: Info
Prints a message to the Console.
console.log('log');
console.log() example above.
console.table(array)
Log level: Info
Logs an array of objects as a table.
console.table([
{
first: 'René',
last: 'Magritte',
},
{
first: 'Chaim',
last: 'Soutine',
birthday: '18930113',
},
{
first: 'Henri',
last: 'Matisse',
}
]);
console.table() example above.
console.time([label])
Starts a new timer. Call console.timeEnd([label]) to stop the timer and
print the elapsed time to the Console.
console.time();
for (var i = 0; i < 100000; i++) {
let square = i ** 2;
}
console.timeEnd();
console.time() example above.
console.timeEnd([label])
Log level: Info
Stops a timer. See console.time().
console.trace()
Log level: Info
Prints a stack trace to the Console.
const first = () => { second(); };
const second = () => { third(); };
const third = () => { fourth(); };
const fourth = () => { console.trace(); };
first();
console.trace() example above.
console.warn(object [, object, ...])
Log level: Warning
Prints a warning to the Console.
console.warn('warn');
console.warn() example above.