ESLintDisallow Extra Parens (no-extra-parens)
This rule restricts the use of parentheses to only where they are necessary. It may be restricted to report only function expressions.
Rule Details
Exceptions
A few cases of redundant parentheses are always allowed:
- RegExp literals:
(/abc/).test(var)is always valid. - IIFEs:
var x = (function () {})();,((function foo() {return 1;})())are always valid.
Options
The default behavior of the rule is specified by "all" and it will report unnecessary parentheses around any expression. The following patterns are considered problems:
/*eslint no-extra-parens: 2*/
a = (b * c); /*error Gratuitous parentheses around expression.*/
(a * b) + c; /*error Gratuitous parentheses around expression.*/
typeof (a); /*error Gratuitous parentheses around expression.*/
The following patterns are not considered problems:
/*eslint no-extra-parens: 2*/
(0).toString();
({}.toString.call());
(function(){} ? a() : b())
(/^a$/).test(x);
If the option is set to "functions", only function expressions will be checked for unnecessary parentheses. The following patterns are considered problems:
/*eslint no-extra-parens: [2, "functions"]*/
((function foo() {}))(); /*error Gratuitous parentheses around expression.*/
var y = (function () {return 1;}); /*error Gratuitous parentheses around expression.*/
The following patterns are not considered problems:
/*eslint no-extra-parens: [2, "functions"]*/
(0).toString();
({}.toString.call());
(function(){} ? a() : b());
(/^a$/).test(x);
a = (b * c);
(a * b) + c;
typeof (a);
Further Reading
Version
This rule was introduced in ESLint 0.1.4.