@studnicky/v8/prototype-modification

Disallows assigning to .prototype (e.g. Foo.prototype.bar = ...). Mutating the prototype after construction invalidates every existing instance's hidden class and prevents inline-cache hits for any code that has already seen the type.

Fixable: No · Options: No · Suggested severity: error

✗ Incorrect

MyClass.prototype.newMethod = function() { /* ... */ };

Array.prototype.last = function() { return this[this.length - 1]; };

✓ Correct

// Declare all methods in the class body
class MyClass {
  newMethod() { /* ... */ }
}

// Use a utility function instead of extending built-ins
function last<T>(arr: T[]): T | undefined {
  return arr[arr.length - 1];
}