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Version: 3.4.0


The console.assert() method writes an error message to the console if the assertion is false. If the assertion is true, nothing happens.


assert(assertion, obj1)
assert(assertion, obj1, obj2)
assert(assertion, obj1, obj2, /* … ,*/ objN)

assert(assertion, msg)
assert(assertion, msg, subst1)
assert(assertion, msg, subst1, /* … ,*/ substN)


  • assertion
    • : Any boolean expression. If the assertion is false, the message is written to the console.
  • obj1objN
    • : 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.
  • subst1substN
    • : JavaScript objects with which to replace substitution strings within msg. This parameter gives you additional control over the format of the output.

Return value