noSwitchDeclarations

诊断类别：lint/correctness/noSwitchDeclarations

¥Diagnostic Category: lint/correctness/noSwitchDeclarations

JavaScript (and super languages)

自从：v1.0.0

¥Since: v1.0.0

来源：

¥Sources:

与以下相同：no-case-declarations

¥Same as: no-case-declarations

禁止在 switch 子句中使用词汇声明。

¥Disallow lexical declarations in switch clauses.

switch 子句中的词汇声明可在整个 switch 中访问。但是，它仅在分配时才会初始化，这只有在到达定义它的 switch 子句时才会发生。

¥Lexical declarations in switch clauses are accessible in the entire switch. However, it only gets initialized when it is assigned, which will only happen if the switch clause where it is defined is reached.

要确保词汇声明仅适用于当前 switch 子句，请将声明封装在块中。

¥To ensure that the lexical declarations only apply to the current switch clause wrap your declarations in a block.

示例

¥Examples

无效

¥Invalid

switch (foo) {
    case 0:
        const x = 1;
        break;
    case 2:
        x; // `x` can be used while it is not initialized
        break;
}

code-block.js:3:9 lint/correctness/noSwitchDeclarations  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Other switch clauses can erroneously access this declaration.
    Wrap the declaration in a block to restrict its access to the switch clause.
  
    1 │ switch (foo) {
    2 │     case 0:
  > 3 │         const x = 1;
      │         ^^^^^^^^^^^
    4 │         break;
    5 │     case 2:
  
  ℹ The declaration is defined in this switch clause:
  
    1 │ switch (foo) {
  > 2 │     case 0:
      │     ^^^^^^^
  > 3 │         const x = 1;
  > 4 │         break;
      │         ^^^^^^
    5 │     case 2:
    6 │         x; // x can be used while it is not initialized
  
  ℹ Unsafe fix: Wrap the declaration in a block.
  
    1  1 │   switch (foo) {
    2    │ - ····case·0:
       2 │ + ····case·0:·{
    3  3 │           const x = 1;
    4    │ - ········break;
       4 │ + ········break;
       5 │ + ····}
    5  6 │       case 2:
    6  7 │           x; // x can be used while it is not initialized

switch (foo) {
    case 0:
        function f() {}
        break;
    case 2:
        f(); // `f` can be called here
        break;
}

code-block.js:3:9 lint/correctness/noSwitchDeclarations  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Other switch clauses can erroneously access this declaration.
    Wrap the declaration in a block to restrict its access to the switch clause.
  
    1 │ switch (foo) {
    2 │     case 0:
  > 3 │         function f() {}
      │         ^^^^^^^^^^^^^^^
    4 │         break;
    5 │     case 2:
  
  ℹ The declaration is defined in this switch clause:
  
    1 │ switch (foo) {
  > 2 │     case 0:
      │     ^^^^^^^
  > 3 │         function f() {}
  > 4 │         break;
      │         ^^^^^^
    5 │     case 2:
    6 │         f(); // f can be called here
  
  ℹ Unsafe fix: Wrap the declaration in a block.
  
    1  1 │   switch (foo) {
    2    │ - ····case·0:
       2 │ + ····case·0:·{
    3  3 │           function f() {}
    4    │ - ········break;
       4 │ + ········break;
       5 │ + ····}
    5  6 │       case 2:
    6  7 │           f(); // f can be called here

switch (foo) {
    case 0:
        class A {}
        break;
    default:
        new A(); // `A` can be instantiated here
        break;
}

code-block.js:3:9 lint/correctness/noSwitchDeclarations  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Other switch clauses can erroneously access this declaration.
    Wrap the declaration in a block to restrict its access to the switch clause.
  
    1 │ switch (foo) {
    2 │     case 0:
  > 3 │         class A {}
      │         ^^^^^^^^^^
    4 │         break;
    5 │     default:
  
  ℹ The declaration is defined in this switch clause:
  
    1 │ switch (foo) {
  > 2 │     case 0:
      │     ^^^^^^^
  > 3 │         class A {}
  > 4 │         break;
      │         ^^^^^^
    5 │     default:
    6 │         new A(); // A can be instantiated here
  
  ℹ Unsafe fix: Wrap the declaration in a block.
  
    1  1 │   switch (foo) {
    2    │ - ····case·0:
       2 │ + ····case·0:·{
    3  3 │           class A {}
    4    │ - ········break;
       4 │ + ········break;
       5 │ + ····}
    5  6 │       default:
    6  7 │           new A(); // A can be instantiated here

有效

¥Valid

switch (foo) {
    case 0: {
        const x = 1;
        break;
    }
    case 1:
        // `x` is not visible here
        break;
}

noSwitchDeclarations

示例

无效

有效

相关链接