noNestedSwitch (JavaScript)

Language JavaScript (and super languages)

Summary

Diagnostic Category: lint/nursery/noNestedSwitch
This rule doesn’t have a fix.
The default severity of this rule is information.
Sources:
- Same as sonarjs/no-nested-switch

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "nursery": {
5
        "noNestedSwitch": "error"
6
      }
7
    }
8
  }
9
}

Description

Disallow switch statements inside other switch statements.

A switch statement inside another switch statement is hard to read, because it is easy to mix up which case belongs to which switch. Move the inner switch into a separate function, written outside the outer switch, instead.

A switch statement inside a function is still reported when that function is written inside another switch statement.

Examples

Invalid

1
function foo(n, m) {
2
    switch (n) {
3
        case 0:
4
            switch (m) {
5
                case 1:
6
                    break;
7
            }
8
            break;
9
        default:
10
            break;
11
    }
12
}

code-block.js:4:13 lint/nursery/noNestedSwitch ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This switch statement is inside another switch statement.
  
    2 │     switch (n) {
    3 │         case 0:
  > 4 │             switch (m) {
      │             ^^^^^^
    5 │                 case 1:
    6 │                     break;
  
  ℹ The outer switch statement starts here.
  
    1 │ function foo(n, m) {
  > 2 │     switch (n) {
      │     ^^^^^^
    3 │         case 0:
    4 │             switch (m) {
  
  ℹ Nested switch statements are hard to read, because it is easy to mix up which case belongs to which switch.
  
  ℹ Move the inner switch statement into a separate function written outside the outer switch statement.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.

1
switch (n) {
2
    case 0: {
3
        const handle = (m) => {
4
            switch (m) {
5
                case 1:
6
                    break;
7
            }
8
        };
9
        handle(n);
10
        break;
11
    }
12
}

code-block.js:4:13 lint/nursery/noNestedSwitch ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This switch statement is inside another switch statement.
  
    2 │     case 0: {
    3 │         const handle = (m) => {
  > 4 │             switch (m) {
      │             ^^^^^^
    5 │                 case 1:
    6 │                     break;
  
  ℹ The outer switch statement starts here.
  
  > 1 │ switch (n) {
      │ ^^^^^^
    2 │     case 0: {
    3 │         const handle = (m) => {
  
  ℹ Nested switch statements are hard to read, because it is easy to mix up which case belongs to which switch.
  
  ℹ Move the inner switch statement into a separate function written outside the outer switch statement.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.

Valid

1
function foo(n, m) {
2
    switch (n) {
3
        case 0:
4
            bar(m);
5
            break;
6
        default:
7
            break;
8
    }
9
}
10

11
function bar(m) {
12
    switch (m) {
13
        case 1:
14
            break;
15
    }
16
}