unicorn/no-instanceof-builtins Suspicious

🚧 An auto-fix is still under development.

What it does

Disallows the use of instanceof with ECMAScript built-in constructors because:

• it breaks across execution contexts (iframe, Web Worker, Node VM, etc.);
• it is often misleading (e.g. instanceof Array fails for a subclass);
• there is always a clearer and safer alternative (Array.isArray, typeof, Buffer.isBuffer, …).

Why is this bad?

instanceof breaks across execution contexts (iframe, Web Worker, Node vm), and may give misleading results for subclasses or exotic objects.

Examples

Examples of incorrect code for this rule:

if (arr instanceof Array) { … }
if (el instanceof HTMLElement) { … }

Examples of correct code for this rule:

if (Array.isArray(arr)) { … }
if (el?.nodeType === 1) { … }

How to use

To enable this rule in the CLI or using the config file, you can use:

CLI

oxlint --deny unicorn/no-instanceof-builtins

Config (.oxlintrc.json)

{
  "rules": {
    "unicorn/no-instanceof-builtins": "error"
  }
}

References

• Rule Source