useSimplifiedBooleanReturn (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v2.6.0
Diagnostic Category: lint/nursery/useSimplifiedBooleanReturn
This rule has a safe fix.
The default severity of this rule is information.
Sources:
- Same as unicorn/prefer-boolean-return

How to configure

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{
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  "linter": {
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    "rules": {
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      "nursery": {
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        "useSimplifiedBooleanReturn": "error"
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      }
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    }
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  }
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}

Description

Return conditions directly instead of using if statements that only return true or false.

An if statement whose branches only return true and false is a long way of returning the condition itself. The same applies to an if statement that returns true or false, followed directly by a return of the opposite value. Returning the condition directly is shorter and easier to read.

When the condition doesn’t always produce a boolean, the fix converts it with !! so the function still returns true or false.

A sequence of early returns that all return the same value is not reported, because rewriting only the last one would break up the group:

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function isEmpty(value) {
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    if (value === null) {
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        return true;
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    }
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    if (value === "") {
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        return true;
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    }
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    return false;
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}

Examples

Invalid

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function isPositive(value) {
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    if (value > 0) {
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        return true;
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    }
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    return false;
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}

code-block.js:2:5 lint/nursery/useSimplifiedBooleanReturn  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This if statement only returns true or false.
  
    1 │ function isPositive(value) {
  > 2 │     if (value > 0) {
      │     ^^^^^^^^^^^^^^^^
  > 3 │         return true;
  > 4 │     }
  > 5 │     return false;
      │     ^^^^^^^^^^^^^
    6 │ }
    7 │ 
  
  ℹ Returning the condition directly is shorter and easier to read.
  
  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.
  
  ℹ Safe fix: Return the condition directly.
  
    1 1 │   function isPositive(value) {
    2   │ - ····if·(value·>·0)·{
    3   │ - ········return·true;
    4   │ - ····}
    5   │ - ····return·false;
      2 │ + ····return·value·>·0;
    6 3 │   }
    7 4 │

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function hasItems(items) {
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    if (items.length) {
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        return true;
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    } else {
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        return false;
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    }
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}

code-block.js:2:5 lint/nursery/useSimplifiedBooleanReturn  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This if statement only returns true or false.
  
    1 │ function hasItems(items) {
  > 2 │     if (items.length) {
      │     ^^^^^^^^^^^^^^^^^^^
  > 3 │         return true;
  > 4 │     } else {
  > 5 │         return false;
  > 6 │     }
      │     ^
    7 │ }
    8 │ 
  
  ℹ Returning the condition directly is shorter and easier to read.
  
  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.
  
  ℹ Safe fix: Return the condition directly.
  
    1 1 │   function hasItems(items) {
    2   │ - ····if·(items.length)·{
    3   │ - ········return·true;
    4   │ - ····}·else·{
    5   │ - ········return·false;
    6   │ - ····}
      2 │ + ····return·!!items.length;
    7 3 │   }
    8 4 │

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function isNotPositive(value) {
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    if (value > 0) {
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        return false;
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    }
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    return true;
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}

code-block.js:2:5 lint/nursery/useSimplifiedBooleanReturn  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ℹ This if statement only returns true or false.
  
    1 │ function isNotPositive(value) {
  > 2 │     if (value > 0) {
      │     ^^^^^^^^^^^^^^^^
  > 3 │         return false;
  > 4 │     }
  > 5 │     return true;
      │     ^^^^^^^^^^^^
    6 │ }
    7 │ 
  
  ℹ Returning the condition directly is shorter and easier to read.
  
  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.
  
  ℹ Safe fix: Return the condition directly.
  
    1 1 │   function isNotPositive(value) {
    2   │ - ····if·(value·>·0)·{
    3   │ - ········return·false;
    4   │ - ····}
    5   │ - ····return·true;
      2 │ + ····return·!(value·>·0);
    6 3 │   }
    7 4 │

Valid

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function isPositive(value) {
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    return value > 0;
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}
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function hasItems(items) {
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    return !!items.length;
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}
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function check(value) {
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    if (value > 0) {
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        return true;
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    }
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    log(value);
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    return false;
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}