Unused Function Parameters ?

Proposal details

Stage: Unstaged
Status: Inactive
ECMAScript edition: —
Synchronized: Aug 28, 2026
中文译文 · Source repository

Proposal overview

This proposal addresses the problem of unused function parameters in JavaScript, which currently require placeholder names like _ that may conflict with existing code or linters. It explores three main solutions: elisions (empty parameter slots), placeholder syntax (e.g., ? or *), and a placeholder identifier (e.g., _) with early error rules. The proposal is at an early exploratory stage, presenting multiple design options without a selected direction.

Note

The README below comes from the upstream repository and may contain outdated stage or status metadata. Use the proposal details above as the current source of truth.

Unused Function Parameters

The Problem

doSomething((unused1, unused2, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

doSomething((_, __, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

Solutions

Elisions

doSomething(( , , somethingUseful) => {
  doSomethingWith(somethingUseful);
});

Matches with existing destructuring
- ([, c]) is already valid
Some might say it looks weird

Placeholder Syntax

doSomething((?, ?, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

doSomething((*, *, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

// etc.

Most explicit, clearly "using up" a parameter without binding it
Requires more syntax

Placeholder Identifier

doSomething((_, _, somethingUseful) => {
  doSomethingWith(somethingUseful);
});

doSomething((_, _, somethingUseful) => {
  print(_); // IdentifierReference : `_` early error?
  doSomethingWith(somethingUseful);
});

Arguably most natural, other languages use this (C#, Rust, etc.)
Any valid identifiers are already valid identifiers, could conflict with existing code

#Unused Function Parameters ?

#Unused Function Parameters

#The Problem

#Solutions

#Elisions

#Placeholder Syntax