noConfusingLabels

JavaScript (and super languages)

Summary

Rule available since: v1.0.0
Diagnostic Category: lint/suspicious/noConfusingLabels
This rule is recommended, which means is enabled by default.
This rule doesn’t have a fix.
The default severity of this rule is error.
Sources:
- Inspired from no-labels

Description

Disallow labeled statements that are not loops.

Labeled statements in JavaScript are used in conjunction with break and continue to control flow around multiple loops. Their use for other statements is suspicious and unfamiliar.

The rule ignores reactive Svelte statements in Svelte components.

Examples

Invalid

1
label: f();

code-block.js:1:1 lint/suspicious/noConfusingLabels ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected label.
  
  > 1 │ label: f();
      │ ^^^^^
    2 │ 
  
  ℹ Only loops should be labeled.
    The use of labels for other statements is suspicious and unfamiliar.

1
label: {
2
    f();
3
    break label;
4
}

code-block.js:1:1 lint/suspicious/noConfusingLabels ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected label.
  
  > 1 │ label: {
      │ ^^^^^
    2 │     f();
    3 │     break label;
  
  ℹ Only loops should be labeled.
    The use of labels for other statements is suspicious and unfamiliar.

1
label: if (a) {
2
    f()
3
    break label;
4
}

code-block.js:1:1 lint/suspicious/noConfusingLabels ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected label.
  
  > 1 │ label: if (a) {
      │ ^^^^^
    2 │     f()
    3 │     break label;
  
  ℹ Only loops should be labeled.
    The use of labels for other statements is suspicious and unfamiliar.

1
label: switch (a) {
2
    case 0:
3
        break label;
4
}

code-block.js:1:1 lint/suspicious/noConfusingLabels ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Unexpected label.
  
  > 1 │ label: switch (a) {
      │ ^^^^^
    2 │     case 0:
    3 │         break label;
  
  ℹ Only loops should be labeled.
    The use of labels for other statements is suspicious and unfamiliar.

Valid

1
outer: while (a) {
2
    while(b) {
3
        break outer;
4
    }
5
}

1
<script>
2
$: { /* reactive block */ }
3
</script>

Options

Use the options to allow specific labels in your code. Labels can be used to mark code that should be removed under certain conditions, such as in production builds. Some bundlers, such as esbuild and Vite, can be configured to remove labeled statements.

1
{
2
    "options": {
3
        "allowedLabels": ["DEV"]
4
    }
5
}

1
DEV: assertSomeCondition();

How to configure

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