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Diffstat (limited to 'docs/code-quality/lint/linters/eslint-plugin-mozilla/use-isInstance.rst')
| -rw-r--r-- | docs/code-quality/lint/linters/eslint-plugin-mozilla/use-isInstance.rst | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/docs/code-quality/lint/linters/eslint-plugin-mozilla/use-isInstance.rst b/docs/code-quality/lint/linters/eslint-plugin-mozilla/use-isInstance.rst new file mode 100644 index 0000000000..dca1e51c82 --- /dev/null +++ b/docs/code-quality/lint/linters/eslint-plugin-mozilla/use-isInstance.rst @@ -0,0 +1,42 @@ +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`` +- ``*.jsm.js`` +- ``*.xhtml`` with ``there.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 not ``SpecialPowers.ChromeUtils`` +- ``BrowserTestUtils``, ``PlacesUtils`` +- ``document.createXULElement`` +- ``loader.lazyRequireGetter`` +- ``Services.foo``, but not ``SpecialPowers.Services.foo`` + +Examples of incorrect code for this rule: +----------------------------------------- + +.. code-block:: js + + node instanceof Node + text instanceof win.Text + target instanceof this.contentWindow.HTMLAudioElement + +Examples of correct code for this rule: +--------------------------------------- + +.. code-block:: js + + Node.isInstance(node) + win.Text.isInstance(text) + this.contentWindow.HTMLAudioElement.isInstance(target) |