useOptionalChain

Diagnostic Category: lint/complexity/useOptionalChain

JavaScript (and super languages)

Since: v1.0.0

Sources:

Same as: @typescript-eslint/prefer-optional-chain

Description

Enforce using concise optional chain instead of chained logical expressions.

TypeScript 3.7 introduced support for the optional chain operator, which was later standardized and included in the ECMAScript specification. This operator allows you to safely access properties and methods on objects when they are potentially null or undefined. The optional chain operator only chains when the property value is null or undefined. It is much safer than relying upon logical operator chaining; which chains on any truthy value.

Examples

Invalid

foo && foo.bar && foo.bar.baz && foo.bar.baz.buzz

code-block.js:1:1 lint/complexity/useOptionalChain  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Change to an optional chain.
  
  > 1 │ foo && foo.bar && foo.bar.baz && foo.bar.baz.buzz
      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Unsafe fix: Change to an optional chain.
  
    1   │ - foo·&&·foo.bar·&&·foo.bar.baz·&&·foo.bar.baz.buzz
      1 │ + foo?.bar?.baz?.buzz
    2 2 │

foo.bar && foo.bar.baz.buzz

code-block.js:1:1 lint/complexity/useOptionalChain  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Change to an optional chain.
  
  > 1 │ foo.bar && foo.bar.baz.buzz
      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Unsafe fix: Change to an optional chain.
  
    1   │ - foo.bar·&&·foo.bar.baz.buzz
      1 │ + foo.bar?.baz.buzz
    2 2 │

foo !== undefined && foo.bar != undefined && foo.bar.baz !== null && foo.bar.baz.buzz

code-block.js:1:1 lint/complexity/useOptionalChain  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Change to an optional chain.
  
  > 1 │ foo !== undefined && foo.bar != undefined && foo.bar.baz !== null && foo.bar.baz.buzz
      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Unsafe fix: Change to an optional chain.
  
    1   │ - foo·!==·undefined·&&·foo.bar·!=·undefined·&&·foo.bar.baz·!==·null·&&·foo.bar.baz.buzz
      1 │ + foo?.bar?.baz?.buzz
    2 2 │

((foo || {}).bar || {}).baz;

code-block.js:1:1 lint/complexity/useOptionalChain  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Change to an optional chain.
  
  > 1 │ ((foo || {}).bar || {}).baz;
      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Unsafe fix: Change to an optional chain.
  
    1   │ - ((foo·||·{}).bar·||·{}).baz;
      1 │ + foo?.bar?.baz;
    2 2 │

(await (foo1 || {}).foo2 || {}).foo3;

code-block.js:1:1 lint/complexity/useOptionalChain  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Change to an optional chain.
  
  > 1 │ (await (foo1 || {}).foo2 || {}).foo3;
      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Unsafe fix: Change to an optional chain.
  
    1   │ - (await·(foo1·||·{}).foo2·||·{}).foo3;
      1 │ + (await·foo1?.foo2)?.foo3;
    2 2 │

(((typeof x) as string) || {}).bar;

code-block.ts:1:1 lint/complexity/useOptionalChain  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Change to an optional chain.
  
  > 1 │ (((typeof x) as string) || {}).bar;
      │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Unsafe fix: Change to an optional chain.
  
    1   │ - (((typeof·x)·as·string)·||·{}).bar;
      1 │ + ((typeof·x)·as·string)?.bar;
    2 2 │

Valid

foo && bar;

foo || {};

(foo = 2 || {}).bar;

foo || foo.bar;

foo["some long"] && foo["some long string"].baz

How to configure

{
  "linter": {
    "rules": {
      "complexity": {
        "useOptionalChain": "error"
      }
    }
  }
}