eslint/arrow-body-style Style

🚧 An auto-fix is planned for this rule, but not implemented at this time.

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