Console.assert()

Writes an error message to the console if the assertion is false. If the assertion is true, nothing happens.

Note: This feature is available in Web Workers.

Note: The console.assert() method is implemented differently in Node.js than the console.assert() method available in browsers.

Specifically, in browsers, calling console.assert() with a falsy assertion will cause the message to be printed to the console without interrupting execution of subsequent code. In Node.js, however, a falsy assertion will cause an AssertionError to be thrown.

Syntax

console.assert(assertion, obj1 [, obj2, ..., objN]);
console.assert(assertion, msg [, subst1, ..., substN]); // c-like message formatting

Parameters

assertion: Any boolean expression. If the assertion is false, the message is written to the console.
obj1 ... objN: A list of JavaScript objects to output. The string representations of each of these objects are appended together in the order listed and output.
msg: A JavaScript string containing zero or more substitution strings.
subst1 ... substN: JavaScript objects with which to replace substitution strings within msg. This parameter gives you additional control over the format of the output.

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

Specifications

Specification	Status	Comment
Console API The definition of 'console.assert()' in that specification.	Living Standard	Initial definition

Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic support	(Yes)	(Yes)	28.0 (28.0)	(Yes)	(Yes)	(Yes)
Available in workers	(Yes)	(Yes)	38.0 (38.0)	(Yes)	(Yes)	(Yes)
c-like message formatting	No support	?	28.0 (28.0)	?	?	?

Feature	Android	Edge	Firefox Mobile (Gecko)	IE Mobile	Opera Mobile	Safari Mobile
Basic support	?	(Yes)	28.0 (28.0)	?	?	?
Available in workers	?	(Yes)	38.0 (38.0)	?	?	?
c-like message formatting	?	?	28.0 (28.0)	?	?	?

Syntax

Parameters

Specifications

Browser compatibility

See also

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