arrow-body-style.md

Require braces in arrow function body (arrow-body-style)

Arrow functions have two syntactic forms for their function bodies. They may be defined with a block body (denoted by curly braces) () => { ... } or with a single expression () => ..., whose value is implicitly returned.

Rule Details

This rule can enforce or disallow the use of braces around arrow function body.

Options

The rule takes one option, a string, which can be:

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

"always"

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

When the rule is set to "always" the following patterns are considered problems:

/*eslint arrow-body-style: ["error", "always"]*/
/*eslint-env es6*/
let foo = () => 0;

The following patterns are not considered problems:

let foo = () => {
    return 0;
};
let foo = (retv, name) => {
    retv[name] = true;
    return retv;
};

"as-needed"

When the rule is set to "as-needed" the following patterns are considered problems:

/*eslint arrow-body-style: ["error", "as-needed"]*/
/*eslint-env es6*/

let foo = () => {
    return 0;
};
let foo = () => {
    return {
       bar: {
            foo: 1,
            bar: 2,
        }
    };
};

The following patterns are not considered problems:

/*eslint arrow-body-style: ["error", "as-needed"]*/
/*eslint-env es6*/

let foo = () => 0;
let foo = (retv, name) => {
    retv[name] = true;
    return retv;
};
let foo = () => ({
    bar: {
        foo: 1,
        bar: 2,
    }
});
let foo = () => { bar(); };
let foo = () => {};
let foo = () => { /* do nothing */ };
let foo = () => {
    // do nothing.
};

"never"

When the rule is set to "never" the following patterns are considered problems:

/*eslint arrow-body-style: ["error", "never"]*/
/*eslint-env es6*/

let foo = () => {
    return 0;
};
let foo = (retv, name) => {
    retv[name] = true;
    return retv;
};

The following patterns are not considered problems:

/*eslint arrow-body-style: ["error", "never"]*/
/*eslint-env es6*/

let foo = () => 0;
let foo = () => ({ foo: 0 });