This feature is well established and works across many devices and browser versions. It’s been available across browsers since August 2016.
The validationMessage read-only property of the HTMLOutputElement interface returns a string representing a localized message that describes the validation constraints that the <output> control does not satisfy (if any). This is the empty string as <output> elements are not candidates for constraint validation (HTMLOutputElement.willValidate is false).
The empty string, "";
| Specification |
|---|
| HTML> # dom-cva-validationmessage-dev> |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
validationMessage |
9 | 14 | 4 | ≤12.1 | 5.1 | 18 | 4 | ≤12.1 | 5 | 1.0 | 3 | 5 |
<output>HTMLOutputElementHTMLOutputElement.willValidateHTMLOutputElement.validityHTMLOutputElement.checkValidity()HTMLOutputElement.reportValidity()HTMLOutputElement.setCustomValidity():valid and :invalid pseudo-classes
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https://developer.mozilla.org/en-US/docs/Web/API/HTMLOutputElement/validationMessage