Unfiltered for..in loop

Reports unfiltered for-in loops.

The use of this construct results in processing not only own properties of an object but properties from its prototype as well. It may be unexpected in some specific cases, for example, in utility methods that copy or modify all properties or when Object's prototype may be incorrectly modified. For example, the following code will print 42 and myMethod:

Object.prototype.myMethod = function myMethod() {};
let a = { foo: 42 };
for (let i in a) {
  console.log(a[i]);
}

Suggests replacing the whole loop with a Object.keys() method or adding a hasOwnProperty() check. After applying the quick-fix the code looks as follows:

for (let i in a) {
  if (a.hasOwnProperty(i)) {
    console.log(a[i]);
  }
}

Inspection options

Option	Type	Default
Skip iterations over reference with array or object initializer	Checkbox	true

Inspection Details
Available in:	AppCode 2023.3, CLion 2023.3, GoLand 2023.3, IntelliJ IDEA 2023.3, JetBrains Rider 2023.1, PhpStorm 2023.3, PyCharm 2023.3, Qodana for .NET 2023.1, Qodana for JS 2023.3, Qodana for JVM 2023.3, Qodana for PHP 2023.3, Qodana for Ruby 2023.3, RubyMine 2023.3, WebStorm 2023.3
Plugin:	JavaScript and TypeScript, 233.SNAPSHOT

Last modified: 13 July 2023