Marko Denic
Marko Denic

Marko Denic

Use console.log() like a pro!

Use console.log() like a pro!

Featured on Hashnode
Featured on daily.dev
Marko Denic

Published on Nov 23, 2020

3 min read

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 varies from browser to browser, but there is a de facto set of features that are typically provided.

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.
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Custom CSS styles for a console.log()

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

String substitutions

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

%sstring
%i or %dinteger
%o or %0object
%ffloat
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console.assert()

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

console.clear()

Clear the console. Alt Text

console.count()

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

console.dir()

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

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(). Alt Text

HTML elements in the console

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console.memory

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

Note: memory is a property and not a method. Alt Text

console.table()

Displays tabular data as a table. Alt Text

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. Alt Text

console.trace()

Outputs a stack trace. Alt Text

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