noUnsafeOptionalChaining (JavaScript)
Language JavaScript (and super languages)
Summary
Section titled “Summary”- Rule available since:
v1.0.0 - Diagnostic Category:
lint/correctness/noUnsafeOptionalChaining - This rule is recommended, meaning it is enabled by default.
- This rule doesn’t have a fix.
- The default severity of this rule is error.
- Sources:
- Same as
no-unsafe-optional-chaining
- Same as
How to configure
Section titled “How to configure”{ "linter": { "rules": { "correctness": { "noUnsafeOptionalChaining": "error" } } }}Description
Section titled “Description”Disallow optional chaining where undefined is not a valid result.
When the value before ?. is null or undefined, JavaScript stops evaluating that chain
and returns undefined. Calling that result, reading another property from it, or using it
where an object is required can then throw a TypeError.
Parentheses end the protection of an optional chain. For example, (object?.property).name
still tries to read name when object?.property produces undefined.
Examples
Section titled “Examples”Invalid
Section titled “Invalid”1 in obj?.foo;code-block.js:1:9 lint/correctness/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ 1 in obj?.foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ 1 in obj?.foo;
│ ^^^^^^^^^^^^^
2 │
ℹ Optional chaining produces undefined when the value before ?. is null or undefined, and this operation does not accept undefined.
ℹ Provide a fallback value, for example (a?.b ?? {}), or check that the value is defined before using it.
with (obj?.foo);code-block.cjs:1:10 lint/correctness/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ with (obj?.foo);
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ with (obj?.foo);
│ ^^^^^^^^^^^^^^^^
2 │
ℹ Optional chaining produces undefined when the value before ?. is null or undefined, and this operation does not accept undefined.
ℹ Provide a fallback value, for example (a?.b ?? {}), or check that the value is defined before using it.
for (bar of obj?.foo);code-block.js:1:16 lint/correctness/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ for (bar of obj?.foo);
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ for (bar of obj?.foo);
│ ^^^^^^^^^^^^^^^^^^^^^^
2 │
ℹ Optional chaining produces undefined when the value before ?. is null or undefined, and this operation does not accept undefined.
ℹ Provide a fallback value, for example (a?.b ?? {}), or check that the value is defined before using it.
bar instanceof obj?.foo;code-block.js:1:19 lint/correctness/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ bar instanceof obj?.foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ bar instanceof obj?.foo;
│ ^^^^^^^^^^^^^^^^^^^^^^^
2 │
ℹ Optional chaining produces undefined when the value before ?. is null or undefined, and this operation does not accept undefined.
ℹ Provide a fallback value, for example (a?.b ?? {}), or check that the value is defined before using it.
const { bar } = obj?.foo;code-block.js:1:20 lint/correctness/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ const { bar } = obj?.foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ const { bar } = obj?.foo;
│ ^^^^^^^^^^^^^^^^^^
2 │
ℹ Optional chaining produces undefined when the value before ?. is null or undefined, and this operation does not accept undefined.
ℹ Provide a fallback value, for example (a?.b ?? {}), or check that the value is defined before using it.
(obj?.foo)();code-block.js:1:5 lint/correctness/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ (obj?.foo)();
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ (obj?.foo)();
│ ^^
2 │
ℹ Optional chaining produces undefined when the value before ?. is null or undefined, and this operation does not accept undefined.
ℹ Provide a fallback value, for example (a?.b ?? {}), or check that the value is defined before using it.
(baz?.bar).foo;code-block.js:1:5 lint/correctness/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ (baz?.bar).foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ (baz?.bar).foo;
│ ^^^
2 │
ℹ Optional chaining produces undefined when the value before ?. is null or undefined, and this operation does not accept undefined.
ℹ Provide a fallback value, for example (a?.b ?? {}), or check that the value is defined before using it.
(obj?.foo)?.();obj?.foo();(obj?.foo ?? bar)();obj?.foo.bar;obj.foo?.bar;foo?.()?.bar;Related links
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