This rule restricts the use of parentheses to only where they are necessary.
This rule always ignores extra parentheses around the following:
- RegExp literals such as
(/abc/).test(var)
to avoid conflicts with the wrap-regex rule - immediately-invoked function expressions (also known as IIFEs) such as
var x = (function () {})();
and((function foo() {return 1;})())
to avoid conflicts with the wrap-iife rule - arrow function arguments to avoid conflicts with the arrow-parens rule
This rule has a string option:
"all"
(default) disallows unnecessary parentheses around any expression"functions"
disallows unnecessary parentheses only around function expressions
This rule has an object option for exceptions to the "all"
option:
"conditionalAssign": false
allows extra parentheses around assignments in conditional test expressions"returnAssign": false
allows extra parentheses around assignments inreturn
statements"nestedBinaryExpressions": false
allows extra parentheses in nested binary expressions"ignoreJSX": "none|all|multi-line|single-line"
allows extra parentheses around no/all/multi-line/single-line JSX components. Defaults tonone
."enforceForArrowConditionals": false
allows extra parentheses around ternary expressions which are the body of an arrow function
Examples of incorrect code for this rule with the default "all"
option:
/* eslint no-extra-parens: "error" */
a = (b * c);
(a * b) + c;
for (a in (b, c));
for (a in (b));
for (a of (b));
typeof (a);
(function(){} ? a() : b());
Examples of correct code for this rule with the default "all"
option:
/* eslint no-extra-parens: "error" */
(0).toString();
(Object.prototype.toString.call());
({}.toString.call());
(function(){}) ? a() : b();
(/^a$/).test(x);
for (a of (b, c));
for (a of b);
for (a in b, c);
for (a in b);
Examples of correct code for this rule with the "all"
and { "conditionalAssign": false }
options:
/* eslint no-extra-parens: ["error", "all", { "conditionalAssign": false }] */
while ((foo = bar())) {}
if ((foo = bar())) {}
do; while ((foo = bar()))
for (;(a = b););
Examples of correct code for this rule with the "all"
and { "returnAssign": false }
options:
/* eslint no-extra-parens: ["error", "all", { "returnAssign": false }] */
function a(b) {
return (b = 1);
}
function a(b) {
return b ? (c = d) : (c = e);
}
b => (b = 1);
b => b ? (c = d) : (c = e);
Examples of correct code for this rule with the "all"
and { "nestedBinaryExpressions": false }
options:
/* eslint no-extra-parens: ["error", "all", { "nestedBinaryExpressions": false }] */
x = a || (b && c);
x = a + (b * c);
x = (a * b) / c;
Examples of correct code for this rule with the all
and { "ignoreJSX": "all" }
options:
/* eslint no-extra-parens: ["error", "all", { ignoreJSX: "all" }] */
const Component = (<div />)
const Component = (
<div
prop={true}
/>
)
Examples of incorrect code for this rule with the all
and { "ignoreJSX": "multi-line" }
options:
/* eslint no-extra-parens: ["error", "all", { ignoreJSX: "multi-line" }] */
const Component = (<div />)
const Component = (<div><p /></div>)
Examples of correct code for this rule with the all
and { "ignoreJSX": "multi-line" }
options:
/* eslint no-extra-parens: ["error", "all", { ignoreJSX: "multi-line" }] */
const Component = (
<div>
<p />
</div>
)
const Component = (
<div
prop={true}
/>
)
Examples of incorrect code for this rule with the all
and { "ignoreJSX": "single-line" }
options:
/* eslint no-extra-parens: ["error", "all", { ignoreJSX: "single-line" }] */
const Component = (
<div>
<p />
</div>
)
const Component = (
<div
prop={true}
/>
)
Examples of correct code for this rule with the all
and { "ignoreJSX": "single-line" }
options:
/* eslint no-extra-parens: ["error", "all", { ignoreJSX: "single-line" }] */
const Component = (<div />)
const Component = (<div><p /></div>)
Examples of correct code for this rule with the "all"
and { "enforceForArrowConditionals": false }
options:
/* eslint no-extra-parens: ["error", "all", { "enforceForArrowConditionals": false }] */
const b = a => 1 ? 2 : 3;
const d = c => (1 ? 2 : 3);
Examples of incorrect code for this rule with the "functions"
option:
/* eslint no-extra-parens: ["error", "functions"] */
((function foo() {}))();
var y = (function () {return 1;});
Examples of correct code for this rule with the "functions"
option:
/* eslint no-extra-parens: ["error", "functions"] */
(0).toString();
(Object.prototype.toString.call());
({}.toString.call());
(function(){} ? a() : b());
(/^a$/).test(x);
a = (b * c);
(a * b) + c;
typeof (a);