no-unsafe-optional-chaining.md

disallow optional chaining that possibly errors (no-unsafe-optional-chaining)

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

Rule Details

This rule disallows some cases that might be an TypeError.

Examples of incorrect code for this rule:

/*eslint no-unsafe-optional-chaining: "error"*/

(obj?.foo)();

(obj?.foo).bar;

(obj?.foo)`template`;

new (obj?.foo)();

[...obj?.foo];

bar(...obj?.foo);

Examples of correct code for this rule:

/*eslint no-unsafe-optional-chaining: "error"*/

(obj?.foo)?.();

obj?.foo?.bar;

(obj?.foo ?? bar)`template`;

new (obj?.foo ?? bar)();

var baz = {...obj.?foo};

Options

This rule has an object option:

• disallowArithmeticOperators: Disallow arithmetic operation on optional chaining expression (Default false). If this is true, this rule warns arithmetic operations on optional chaining expression which possibly result in NaN.

disallowArithmeticOperators

Examples of additional incorrect code for this rule with the { "disallowArithmeticOperators": true } option:

/*eslint no-unsafe-optional-chaining: ["error", { "disallowArithmeticOperators": true }]*/

obj?.foo + bar;

obj?.foo * bar;

+obj?.foo;

baz += obj?.foo;