Console.assert()
Writes an error message to the console if the assertion is false. If the assertion is true, nothing happens.
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. |
Editor's Draft | Initial definition |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) | 28.0 (28.0) | (Yes) | (Yes) | (Yes) |
Available in workers | (Yes) | 38.0 (38.0) | (Yes) | (Yes) | (Yes) |
c-like message formatting | No support | 28.0 (28.0) | ? | ? | ? |
Feature | Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|
Basic support | ? | 28.0 (28.0) | ? | ? | ? |
Available in workers | ? | 38.0 (38.0) | ? | ? | ? |
c-like message formatting | ? | 28.0 (28.0) | ? | ? | ? |
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
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/console/assert