ESLintRequire 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 or two options. The first is 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)
The second one is an object for more fine-grained configuration when the first option is "as-needed". Currently, the only available option is requireReturnForObjectLiteral, a boolean property. It’s false by default. If set to true, it requires braces and an explicit return for object literals.
"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.
};
let foo = () => ({ bar: 0 });
requireReturnForObjectLiteral
When the rule is set to "as-needed", { requireReturnForObjectLiteral: true } the following patterns are considered problems:
/*eslint arrow-body-style: ["error", "as-needed", { requireReturnForObjectLiteral: true }]*/
/*eslint-env es6*/
let foo = () => ({});
let foo = () => ({ bar: 0 });
The following patterns are not considered problems:
/*eslint arrow-body-style: ["error", "as-needed", { requireReturnForObjectLiteral: true }]*/
/*eslint-env es6*/
let foo = () => {};
let foo = () => { return { bar: 0 }; };
“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 });
Version
This rule was introduced in ESLint 1.8.0.