eslint/no-extend-native Suspicious

What it does

Prevents extending native global objects such as Object, String, or Array with new properties.

Why is this bad?

Extending native objects can cause unexpected behavior and conflicts with other code.

For example:

// Adding a new property, which might seem okay
Object.prototype.extra = 55;

// Defining a user object
const users = {
  1: "user1",
  2: "user2",
};

for (const id in users) {
  // This will print "extra" as well as "1" and "2":
  console.log(id);
}

Examples

Examples of incorrect code for this rule:

Object.prototype.p = 0;
Object.defineProperty(Array.prototype, "p", { value: 0 });

Examples of correct code for this rule:

x.prototype.p = 0;
Object.defineProperty(x.prototype, "p", { value: 0 });

References

• Rule Source