Disallow Unnecessary Nested Blocks (no-lone-blocks)
In JavaScript, prior to ES6, standalone code blocks delimited by curly braces do not create a new scope and have no use. For example, these curly braces do nothing to foo
:
{
var foo = bar();
}
In ES6, code blocks may create a new scope if a block-level binding (let
and const
), a class declaration or a function declaration (in strict mode) are present. A block is not considered redundant in these cases.
Rule Details
This rule aims to eliminate unnecessary and potentially confusing blocks at the top level of a script or within other blocks.
Examples of incorrect code for this rule:
/*eslint no-lone-blocks: "error"*/
{}
if (foo) {
bar();
{
baz();
}
}
function bar() {
{
baz();
}
}
{
function foo() {}
}
{
aLabel: {
}
}
Examples of correct code for this rule with es6 environment:
/*eslint no-lone-blocks: "error"*/
/*eslint-env es6*/
while (foo) {
bar();
}
if (foo) {
if (bar) {
baz();
}
}
function bar() {
baz();
}
{
let x = 1;
}
{
const y = 1;
}
{
class Foo {}
}
aLabel: {
}
Examples of correct code for this rule with es6 environment and strict mode via "parserOptions": { "sourceType": "module" }
in the ESLint configuration or "use strict"
directive in the code:
/*eslint no-lone-blocks: "error"*/
/*eslint-env es6*/
"use strict";
{
function foo() {}
}
Version
This rule was introduced in ESLint 0.4.0.