use-isInstance¶
Prefer .isInstance()
in chrome scripts over the standard instanceof
operator for DOM interfaces, since the latter will return false when the object
is created from a different context.
These files are covered:
*.sys.mjs
*.jsm
*.xhtml
withthere.is.only.xul
*.js
with a heuristic
Since there is no straightforward way to detect chrome scripts, currently the linter assumes that any script including the following words are chrome privileged. This of course may not be sufficient and is open for change:
ChromeUtils
, but notSpecialPowers.ChromeUtils
BrowserTestUtils
,PlacesUtils
document.createXULElement
loader.lazyRequireGetter
Services.foo
, but notSpecialPowers.Services.foo
Examples of incorrect code for this rule:¶
node instanceof Node
text instanceof win.Text
target instanceof this.contentWindow.HTMLAudioElement
Examples of correct code for this rule:¶
Node.isInstance(node)
win.Text.isInstance(text)
this.contentWindow.HTMLAudioElement.isInstance(target)