noUnusedFunctionParameters

Diagnostic Category: lint/correctness/noUnusedFunctionParameters

JavaScript (and super languages)

Since: v1.8.0

Description

Disallow unused function parameters.

There is an exception to this rule: parameters that starts with underscore, e.g. function foo(_a, _b) {}.

Examples

Invalid

function foo(myVar) {
    console.log('foo');
}

code-block.js:1:14 lint/correctness/noUnusedFunctionParameters  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This parameter is unused.
  
  > 1 │ function foo(myVar) {
      │              ^^^^^
    2 │     console.log(‘foo’);
    3 │ }
  
  ℹ Unused parameters might be the result of an incomplete refactoring.
  
  ℹ Unsafe fix: If this is intentional, prepend myVar with an underscore.
  
    1   │ - function·foo(myVar)·{
      1 │ + function·foo(_myVar)·{
    2 2 │       console.log(‘foo’);
    3 3 │   }

new Promise((accept, reject) => {
    window.setTimeout(accept, 1000);
});

code-block.js:1:22 lint/correctness/noUnusedFunctionParameters  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This parameter is unused.
  
  > 1 │ new Promise((accept, reject) => {
      │                      ^^^^^^
    2 │     window.setTimeout(accept, 1000);
    3 │ });
  
  ℹ Unused parameters might be the result of an incomplete refactoring.
  
  ℹ Unsafe fix: If this is intentional, prepend reject with an underscore.
  
    1   │ - new·Promise((accept,·reject)·=>·{
      1 │ + new·Promise((accept,·_reject)·=>·{
    2 2 │       window.setTimeout(accept, 1000);
    3 3 │   });

const squares = [[1, 1], [2, 4], [3, 9], [4, 16]];
squares.filter(([k, v]) => v > 5);

code-block.js:2:18 lint/correctness/noUnusedFunctionParameters  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ This parameter is unused.
  
    1 │ const squares = [[1, 1], [2, 4], [3, 9], [4, 16]];
  > 2 │ squares.filter(([k, v]) => v > 5);
      │                  ^
    3 │ 
  
  ℹ Unused parameters might be the result of an incomplete refactoring.
  
  ℹ Unsafe fix: If this is intentional, prepend k with an underscore.
  
    1 1 │   const squares = [[1, 1], [2, 4], [3, 9], [4, 16]];
    2   │ - squares.filter(([k,·v])·=>·v·>·5);
      2 │ + squares.filter(([_k,·v])·=>·v·>·5);
    3 3 │

Valid

function foo(myVar) {
    console.log(myVar);
}

How to configure

{
  "linter": {
    "rules": {
      "correctness": {
        "noUnusedFunctionParameters": "error"
      }
    }
  }
}