eslint/no-unsafe-optional-chaining Correctness

✅ This rule is turned on by default.

What it does

Disallow use of optional chaining in contexts where the undefined value is not allowed

Why is this bad?

The optional chaining (?.) expression can short-circuit with a return value of undefined. Therefore, treating an evaluated optional chaining expression as a function, object, number, etc., can cause TypeError or unexpected results. For example:

Example

var obj = undefined;
1 in obj?.foo; // TypeError
with (obj?.foo); // TypeError
for (bar of obj?.foo); // TypeError
bar instanceof obj?.foo; // TypeError
const { bar } = obj?.foo; // TypeError

How to use

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

CLI

oxlint --deny no-unsafe-optional-chaining

Config (.oxlintrc.json)

{
  "rules": {
    "no-unsafe-optional-chaining": "error"
  }
}

References

• Rule Source