eslint/arrow-body-style Style

🚧 An auto-fix is still under development.

What it does

This rule can enforce or disallow the use of braces around arrow function body. Arrow functions can use either:

• a block body () => { ... }
• or a concise body () => expression with an implicit return.

Why is this bad?

Inconsistent use of block vs. concise bodies makes code harder to read. Concise bodies are limited to a single expression, whose value is implicitly returned.

Options

First option:

• Type: string
• Enum: "always", "as-needed", "never"
• Default: "never"

Possible values:

• never enforces no braces where they can be omitted (default)
• always enforces braces around the function body
• as-needed enforces no braces around the function body (constrains arrow functions to the role of returning an expression)

Second option:

• Type: object
• Properties:
  • requireReturnForObjectLiteral: boolean (default: false) - requires braces and an explicit return for object literals.

Note: This option only applies when the first option is "as-needed".

Example configuration:

{
  "arrow-body-style": ["error", "as-needed", { "requireReturnForObjectLiteral": true }]
}

Examples

"never" (default)

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

/* arrow-body-style: ["error", "never"] */

/* ✘ Bad: */
const foo = () => {
  return 0;
};

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

/* arrow-body-style: ["error", "never"] */

/* ✔ Good: */
const foo = () => 0;
const bar = () => ({ foo: 0 });

"always"

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

/* arrow-body-style: ["error", "always"] */

/* ✘ Bad: */
const foo = () => 0;

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

/* arrow-body-style: ["error", "always"] */

/* ✔ Good: */
const foo = () => {
  return 0;
};

"as-needed"

Examples of incorrect code for this rule with the as-needed option:

/* arrow-body-style: ["error", "as-needed"] */

/* ✘ Bad: */
const foo = () => {
  return 0;
};

Examples of correct code for this rule with the as-needed option:

/* arrow-body-style: ["error", "as-needed"] */

/* ✔ Good: */
const foo1 = () => 0;

const foo2 = (retv, name) => {
  retv[name] = true;
  return retv;
};

const foo3 = () => {
  bar();
};

"as-needed" with requireReturnForObjectLiteral

Examples of incorrect code for this rule with the { "requireReturnForObjectLiteral": true } option:

/* arrow-body-style: ["error", "as-needed", { "requireReturnForObjectLiteral": true }]*/

/* ✘ Bad: */
const foo = () => ({});
const bar = () => ({ bar: 0 });

Examples of correct code for this rule with the { "requireReturnForObjectLiteral": true } option:

/* arrow-body-style: ["error", "as-needed", { "requireReturnForObjectLiteral": true }]*/

/* ✔ Good: */
const foo = () => {};
const bar = () => {
  return { bar: 0 };
};

How to use

To enable this rule in the CLI or using the config file, you can use:

CLI

oxlint --deny arrow-body-style

Config (.oxlintrc.json)

{
  "rules": {
    "arrow-body-style": "error"
  }
}

References

• Rule Source