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useOptionalChain (since v1.0.0)

Diagnostic Category: lint/complexity/useOptionalChain

Sources:

Enforce using concise optional chain instead of chained logical expressions.

TypeScript 3.7 added support for the optional chain operator. 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

Section titled Examples

Invalid

Section titled 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

Section titled Valid
foo && bar;
foo || {};
(foo = 2 || {}).bar;
foo || foo.bar;
foo["some long"] && foo["some long string"].baz
Section titled Related links