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object-format

Enforce object literal line format based on property count.

Targeted pattern scope​

This rule checks ObjectExpression nodes with more than one property and enforces single-line or multi-line formatting based on property count.

What this rule reports​

For each object literal with at least two properties:

  • if property count is less than or equal to maxProperties, the object must be on a single line;
  • otherwise, the object must span multiple lines.

Why this rule exists​

Object literals with inconsistent line formatting are harder to scan. A threshold-based policy keeps short objects compact while forcing larger objects to be readable.

❌ Incorrect​

// default maxProperties: 1
const point = { x: 1, y: 2 };

✅ Correct​

// default maxProperties: 1
const point = {
 x: 1,
 y: 2,
};
// with { maxProperties: 2 }
const point = { x: 1, y: 2 };

Behavior and migration notes​

This rule currently reports only and does not provide an autofix.

Adopt in warning mode first, then align formatting manually (or with codemods) before enforcing as error.

Options​

type Options = [
 {
  maxProperties?: number; // default: 1
 },
];
  • maxProperties: maximum number of properties allowed on one line.

Default configuration​

[{ maxProperties: 1 }];

Additional examples​

const pair = { left: 1, right: 2 };
// ✅ valid when configured with { maxProperties: 2 }

const tupleLike = {
 first: 1,
 second: 2,
 third: 3,
};
// ✅ required when maxProperties is 2

ESLint flat config example​

import etcMisc from "eslint-plugin-etc-misc";

export default [
 {
  plugins: { "etc-misc": etcMisc },
  rules: {
   "etc-misc/object-format": "error",
  },
 },
];

When not to use it​

Disable this rule if Prettier (or another formatter) already defines the object wrapping strategy you want and this threshold approach conflicts with it.

Package documentation​

Rule catalog ID: R053

Further reading​

Adoption resources​

  • Start at warning level in CI, then move to error after cleanup.
  • Use focused codemods/autofix batches per package or directory.