The console.assert()
method 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
The console.assert()
method 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
console.assert(assertion, obj1) console.assert(assertion, obj1, obj2, /* ... ,*/ objN) console.assert(assertion, msg) console.assert(assertion, msg, subst1, /* ... ,*/ substN)
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.
The following code example demonstrates the use of a JavaScript object following the assertion:
const errorMsg = 'the # is not even'; for (let number = 2; number <= 5; number += 1) { console.log('the # is ' + number); console.assert(number % 2 === 0, {number: number, errorMsg: errorMsg}); // or, using ES2015 object property shorthand: // console.assert(number % 2 === 0, {number, errorMsg}); } // output: // the # is 2 // the # is 3 // Assertion failed: {number: 3, errorMsg: "the # is not even"} // the # is 4 // the # is 5 // Assertion failed: {number: 5, errorMsg: "the # is not even"}
See Outputting text to the console in the documentation of console
for further details.
Specification |
---|
Console Standard # assert |
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
assert |
1
|
12
|
28
|
8
|
11
|
4
|
≤37
|
18
|
28
|
11
|
3.2
|
1.0
|
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https://developer.mozilla.org/en-US/docs/Web/API/console/assert