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