noUselessUndefinedInitialization

诊断类别：lint/complexity/noUselessUndefinedInitialization

¥Diagnostic Category: lint/complexity/noUselessUndefinedInitialization

JavaScript (and super languages)

自从：v1.7.2

¥Since: v1.7.2

来源：

¥Sources:

与以下相同：no-undef-init

¥Same as: no-undef-init

禁止将变量初始化为 undefined。

¥Disallow initializing variables to undefined.

声明但未初始化为任何值的变量会自动获得 undefined 的值。避免将变量初始化为 undefined 被认为是最佳实践。

¥A variable that is declared and not initialized to any value automatically gets the value of undefined. It’s considered a best practice to avoid initializing variables to undefined.

请注意，在自动修复时，附加到初始化值或变量的任何内联注释都将移动到变量声明的末尾。请注意，这与 Eslint 的行为不同。

¥Please note that any inline comments attached to the initialization value or variable will be moved at the end of the variable declaration on auto-fix. Please be also aware that this differs from Eslint’s behaviour.

示例

¥Examples

无效

¥Invalid

var a = undefined;

code-block.js:1:7 lint/complexity/noUselessUndefinedInitialization  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ It’s not necessary to initialize a to undefined.
  
  > 1 │ var a = undefined;
      │       ^^^^^^^^^^^
    2 │ 
  
  ℹ A variable that is declared and not initialized to any value automatically gets the value of undefined.
  
  ℹ Safe fix: Remove undefined initialization.
  
    1 │ var·a·=·undefined;
      │       -----------

let b = undefined, c = 1, d = 2;

code-block.js:1:7 lint/complexity/noUselessUndefinedInitialization  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ It’s not necessary to initialize b to undefined.
  
  > 1 │ let b = undefined, c = 1, d = 2;
      │       ^^^^^^^^^^^
    2 │ 
  
  ℹ A variable that is declared and not initialized to any value automatically gets the value of undefined.
  
  ℹ Safe fix: Remove undefined initialization.
  
    1 │ let·b·=·undefined,·c·=·1,·d·=·2;
      │       -----------

for (let i = 0; i < 100; i++) {
  let i = undefined;
}

code-block.js:2:8 lint/complexity/noUselessUndefinedInitialization  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ It’s not necessary to initialize i to undefined.
  
    1 │ for (let i = 0; i < 100; i++) {
  > 2 │ 	let i = undefined;
      │ 	      ^^^^^^^^^^^
    3 │ }
    4 │ 
  
  ℹ A variable that is declared and not initialized to any value automatically gets the value of undefined.
  
  ℹ Safe fix: Remove undefined initialization.
  
    2 │ → let·i·=·undefined;
      │         -----------

let f = /**/undefined/**/ ;

code-block.js:1:7 lint/complexity/noUselessUndefinedInitialization  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ It’s not necessary to initialize f to undefined.
  
  > 1 │ let f = /**/undefined/**/ ;
      │       ^^^^^^^^^^^^^^^
    2 │ 
  
  ℹ A variable that is declared and not initialized to any value automatically gets the value of undefined.
  
  ℹ Safe fix: Remove undefined initialization.
  
    1   │ - let·f·=·/**/undefined/**/·;
      1 │ + let·f·;/**//**/
    2 2 │

有效

¥Valid

var a = 1;

class Foo {
  bar = undefined;
}

noUselessUndefinedInitialization

示例

无效

有效

相关链接