#max-lines-per-function

#Configuration

import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'max-lines-per-function': 'error',
    },
  },
]);

Enforce a maximum number of lines of code in a function.

#Rule Details

Long functions are harder to follow than short ones. This rule reports any function whose body — including its declaration line and the closing brace — exceeds the configured line limit.

By default, the rule checks for a maximum of 50 lines per function. Comments and blank lines are counted, and IIFEs are skipped.

Examples of incorrect code for this rule with the default { "max": 50 } option (function body shortened for brevity):

function longFunction() {
  // imagine 50 more lines here
}

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

function shortFunction() {
  doThing();
  return result;
}

#Options

This rule accepts a number (the maximum allowed) or an object with the following properties:

• max (default 50): maximum number of lines a function may contain.
• skipBlankLines (default false): ignore lines made up purely of whitespace.
• skipComments (default false): ignore lines that contain only comments (a line with both code and a comment still counts).
• IIFEs (default false): when true, IIFEs are checked like other functions; when false, they are skipped.

#max

{ "max-lines-per-function": ["error", { "max": 2 }] }

Examples of incorrect code for this rule with { "max": 2 }:

function name() {
  var x = 5;
  var y = 2;
}

Examples of correct code for this rule with { "max": 3 }:

function name() {
  var x = 5;
}

#skipBlankLines

{ "max-lines-per-function": ["error", { "max": 3, "skipBlankLines": true }] }

Examples of correct code for this rule with the above configuration:

function name() {
  var x = 5;

  var y = 2;
}

#skipComments

{ "max-lines-per-function": ["error", { "max": 3, "skipComments": true }] }

Examples of correct code for this rule with the above configuration:

function name() {
  // a comment
  var x = 5;
  var y = 2;
}

#IIFEs

{ "max-lines-per-function": ["error", { "max": 2, "IIFEs": true }] }

Examples of incorrect code for this rule with the above configuration:

(function () {
  var x = 0;
  var y = 0;
})();

#Original Documentation

• https://eslint.org/docs/latest/rules/max-lines-per-function