5 functions of the Console object you didn’t know

This article was originally posted on the Shelly Cloud blog, our Ruby platform as a service that we have decided to shut down on October 2015.

Not everybody knows that apart from the simplest console.log() used for logging, the Console object has a couple of other equally useful function. I have chosen and described the 5 most interesting but unpopular methods, which can be successfully utilized in everyday work.

All of the functions described have been tested and work properly in Google Chrome 38

console.assert(expression, message)

If the value passed in the first argument is false, the function will log a message given as the second argument in the web console. If the expression is true, nothing is logged.

> console.assert(document.querySelector('body'), "Missing 'body' element")

> console.assert(document.querySelector('.foo'), "Missing '.foo' element")
[Error] Assertion failed: Missing '.foo' element


This function displays the provided object or array as a table:


For more details on console.table() see the article "Advanced JavaScript Debugging with console.table()" by Marius Schulz


console.profile(name) starts a CPU profiler in the console. You can use the name of a report as an argument. Each run of the profiler is saved as a separate tab and grouped in a dropdown list. Remember to end profiling using the console.profileEnd().



The console.group(message) groups all logs that follow after it until the console.groupEnd() is called to a dropdown list. Lists can be nested. console.groupCollapsed(message) works analogically, but the created list is collapsed by default.



console.time(name) starts the timer with the name provided as the argument, which counts down the time in milliseconds until it is stopped by the console.timeEnd(name). Exactly the same name must be used in both functions.

> console.time('Saving user')
> console.log('User saved')
> console.timeEnd('Saving user')
Saving user: 2.750ms

More on all functions available can be found in Console API description and article on console usage at the Google Chrome web pages

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