function-paren-newline.md

enforce consistent line breaks inside function parentheses (function-paren-newline)

Many style guides require or disallow newlines inside of function parentheses.

Rule Details

This rule enforces consistent line breaks inside parentheses of function parameters or arguments.

Options

This rule has a single option, which can either be a string or an object.

• "always" requires line breaks inside all function parentheses.
• "never" disallows line breaks inside all function parentheses.
• "multiline" (default) requires linebreaks inside function parentheses if any of the parameters/arguments have a line break between them. Otherwise, it disallows linebreaks.
• "multiline-arguments" works like multiline but allows linebreaks inside function parentheses if there is only one parameter/argument.
• "consistent" requires consistent usage of linebreaks for each pair of parentheses. It reports an error if one parenthesis in the pair has a linebreak inside it and the other parenthesis does not.
• { "minItems": value } requires linebreaks inside function parentheses if the number of parameters/arguments is at least value. Otherwise, it disallows linebreaks.

Example configurations:

{
  "rules": {
    "function-paren-newline": ["error", "never"]
  }
}

{
  "rules": {
    "function-paren-newline": ["error", { "minItems": 3 }]
  }
}

Examples of incorrect code for this rule with the "always" option:

/* eslint function-paren-newline: ["error", "always"] */

function foo(bar, baz) {}

var foo = function(bar, baz) {};

var foo = (bar, baz) => {};

foo(bar, baz);

Examples of correct code for this rule with the "always" option:

/* eslint function-paren-newline: ["error", "always"] */

function foo(
  bar,
  baz
) {}

var foo = function(
  bar, baz
) {};

var foo = (
  bar,
  baz
) => {};

foo(
  bar,
  baz
);

Examples of incorrect code for this rule with the "never" option:

/* eslint function-paren-newline: ["error", "never"] */

function foo(
  bar,
  baz
) {}

var foo = function(
  bar, baz
) {};

var foo = (
  bar,
  baz
) => {};

foo(
  bar,
  baz
);

Examples of correct code for this rule with the "never" option:

/* eslint function-paren-newline: ["error", "never"] */

function foo(bar, baz) {}

function foo(bar,
             baz) {}

var foo = function(bar, baz) {};

var foo = (bar, baz) => {};

foo(bar, baz);

foo(bar,
  baz);

Examples of incorrect code for this rule with the default "multiline" option:

/* eslint function-paren-newline: ["error", "multiline"] */

function foo(bar,
  baz
) {}

var foo = function(
  bar, baz
) {};

var foo = (
  bar,
  baz) => {};

foo(bar,
  baz);

foo(
  function() {
    return baz;
  }
);

Examples of correct code for this rule with the default "multiline" option:

/* eslint function-paren-newline: ["error", "multiline"] */

function foo(bar, baz) {}

var foo = function(
  bar,
  baz
) {};

var foo = (bar, baz) => {};

foo(bar, baz, qux);

foo(
  bar,
  baz,
  qux
);

foo(function() {
  return baz;
});

Examples of incorrect code for this rule with the "consistent" option:

/* eslint function-paren-newline: ["error", "consistent"] */

function foo(bar,
  baz
) {}

var foo = function(bar,
  baz
) {};

var foo = (
  bar,
  baz) => {};

foo(
  bar,
  baz);

foo(
  function() {
    return baz;
  });

Examples of correct code for this rule with the "consistent" option:

/* eslint function-paren-newline: ["error", "consistent"] */

function foo(bar,
  baz) {}

var foo = function(bar, baz) {};

var foo = (
  bar,
  baz
) => {};

foo(
  bar, baz
);

foo(
  function() {
    return baz;
  }
);

Examples of incorrect code for this rule with the "multiline-arguments" option:

/* eslint function-paren-newline: ["error", "multiline-arguments"] */

function foo(bar,
  baz
) {}

var foo = function(bar,
  baz
) {};

var foo = (
  bar,
  baz) => {};

foo(
  bar,
  baz);

foo(
  bar, qux,
  baz
);

Examples of correct code for this rule with the consistent "multiline-arguments" option:

/* eslint function-paren-newline: ["error", "multiline-arguments"] */

function foo(
  bar,
  baz
) {}

var foo = function(bar, baz) {};

var foo = (
  bar
) => {};

foo(
  function() {
    return baz;
  }
);

Examples of incorrect code for this rule with the { "minItems": 3 } option:

/* eslint function-paren-newline: ["error", { "minItems": 3 }] */

function foo(
  bar,
  baz
) {}

function foo(bar, baz, qux) {}

var foo = function(
  bar, baz
) {};

var foo = (bar,
  baz) => {};

foo(bar,
  baz);

Examples of correct code for this rule with the { "minItems": 3 } option:

/* eslint function-paren-newline: ["error", { "minItems": 3 }] */

function foo(bar, baz) {}

var foo = function(
  bar,
  baz,
  qux
) {};

var foo = (
  bar, baz, qux
) => {};

foo(bar, baz);

foo(
  bar, baz, qux
);

When Not To Use It

If don't want to enforce consistent linebreaks inside function parentheses, do not turn on this rule.