useCollapsedElseIf (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v1.1.0
Diagnostic Category: lint/style/useCollapsedElseIf
This rule isn’t recommended, so you need to enable it.
This rule has a safe fix.
The default severity of this rule is information.
Sources:
- Same as no-lonely-if
- Same as collapsible_else_if

How to configure

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{
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  "linter": {
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    "rules": {
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      "style": {
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        "useCollapsedElseIf": "error"
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      }
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    }
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  }
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}

Description

Enforce using else if instead of nested if in else clauses.

If an if statement is the only statement in the else block, it is often clearer to use an else if form.

Examples

Invalid

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if (condition) {
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    // ...
3
} else {
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    if (anotherCondition) {
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        // ...
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    }
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}

code-block.js:3:9 lint/style/useCollapsedElseIf  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This if statement can be collapsed into an else if statement.
  
    1 │ if (condition) {
    2 │     // ...
  > 3 │ } else {
      │         
  > 4 │     if (anotherCondition) {
  > 5 │         // ...
  > 6 │     }
      │     ^
    7 │ }
    8 │ 
  
  ℹ An else block that only contains an if statement adds a level of nesting without need.
  
  ℹ Safe fix: Use collapsed else if instead.
  
    1 1 │   if (condition) {
    2 2 │       // ...
    3   │ - }·else·{
    4   │ - ····if·(anotherCondition)·{
      3 │ + }·else·if·(anotherCondition)·{
    5 4 │           // ...
    6   │ - ····}
    7   │ - }
      5 │ + ····}
    8 6 │

1
if (condition) {
2
    // ...
3
} else {
4
    if (anotherCondition) {
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        // ...
6
    } else {
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        // ...
8
    }
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}

code-block.js:3:9 lint/style/useCollapsedElseIf  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This if statement can be collapsed into an else if statement.
  
     1 │ if (condition) {
     2 │     // ...
   > 3 │ } else {
       │         
   > 4 │     if (anotherCondition) {
   > 5 │         // ...
   > 6 │     } else {
   > 7 │         // ...
   > 8 │     }
       │     ^
     9 │ }
    10 │ 
  
  ℹ An else block that only contains an if statement adds a level of nesting without need.
  
  ℹ Safe fix: Use collapsed else if instead.
  
     1 1 │   if (condition) {
     2 2 │       // ...
     3   │ - }·else·{
     4   │ - ····if·(anotherCondition)·{
       3 │ + }·else·if·(anotherCondition)·{
     5 4 │           // ...
     6 5 │       } else {
     7 6 │           // ...
     8   │ - ····}
     9   │ - }
       7 │ + ····}
    10 8 │

1
if (condition) {
2
    // ...
3
} else {
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    // Comment
5
    if (anotherCondition) {
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        // ...
7
    }
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}

code-block.js:3:9 lint/style/useCollapsedElseIf ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This if statement can be collapsed into an else if statement.
  
    1 │ if (condition) {
    2 │     // ...
  > 3 │ } else {
      │         
  > 4 │     // Comment
  > 5 │     if (anotherCondition) {
  > 6 │         // ...
  > 7 │     }
      │     ^
    8 │ }
    9 │ 
  
  ℹ An else block that only contains an if statement adds a level of nesting without need.

Valid

1
if (condition) {
2
    // ...
3
} else if (anotherCondition) {
4
    // ...
5
}

1
if (condition) {
2
    // ...
3
} else if (anotherCondition) {
4
    // ...
5
} else {
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    // ...
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}

1
if (condition) {
2
    // ...
3
} else {
4
    if (anotherCondition) {
5
        // ...
6
    }
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    doSomething();
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}