console.assert

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

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

Browser compatibility

See also

• WHATWG Console Standard: console.assert
• Opera Dragonfly documentation: Console
• MSDN: Using the F12 Tools Console to View Errors and Status
• Chrome Developer Tools: Using the Console