Use `console.log()` like a pro

Use `console.log()` like a pro
October 03, 2025 | Read time: 4 minutes

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Using console.log() for JavaScript debugging is the most common practice among developers. But there is more.

The console object provides access to the browser’s debugging console. The specifics of how it works vary from browser to browser, but there is a de facto set of features that are typically provided.

I share a ton of JavaScript tips on Twitter, so be sure to check out my profile.

* The most common console methods:

  • console.log(): For general output of logging information.
  • console.info(): Informative logging of information.
  • console.debug(): Outputs a message to the console with the log level debug.
  • console.warn(): Outputs a warning message.
  • console.error(): Outputs an error message.

 

console methods

* Custom CSS styles for a console.log().

The console.log output can be styled in DevTools using the CSS format specifier.

console styled

* String substitutions.

When passing a string to one of the console object’s methods that accepts a string (such as log()), you may use these substitution strings:

  • %s: string
  • %i or %d: integer
  • %o or %O: object
  • %f: float

 

console string substitutions

* console.assert().

Log a message and stack trace to the console if the first argument is false.

console assert

* console.clear().

Clear the console.

console clear

* console.count().

Log the number of times this line has been called with the given label.

console count

* console.dir().

Displays an interactive list of the properties of the specified JavaScript object.

console dir

* console.group() and console.groupEnd().

Creates a new inline group, indenting all following output by another level. To move back out a level, call groupEnd().

console group

* HTML elements in the console:

console html

* console.memory.

The memory property can be used to check out the heap size status.

Note: memory is a property and not a method.

console memory

* console.table().

Displays tabular data as a table.

console table

* console.time() and console.timeEnd().

  • console.time(): Starts a timer with a name specified as an input parameter. Up to 10,000 simultaneous timers can run on a given page.
  • console.timeEnd(): Stops the specified timer and logs the elapsed time in seconds since it started.

console timer

* console.trace().

Outputs a stack trace.

console trace

Which console method did you like the most? Let me know!