disallow unnecessary boolean casts (no-extra-boolean-cast)
The "extends": "eslint:recommended"
property in a configuration file enables this rule.
The --fix
option on the command line can automatically fix some of the problems reported by this rule.
In contexts such as an if
statement's test where the result of the expression will already be coerced to a Boolean, casting to a Boolean via double negation (!!
) or a Boolean
call is unnecessary. For example, these if
statements are equivalent:
if (!!foo) {
// ...
}
if (Boolean(foo)) {
// ...
}
if (foo) {
// ...
}
Rule Details
This rule disallows unnecessary boolean casts.
Examples of incorrect code for this rule:
/*eslint no-extra-boolean-cast: "error"*/
var foo = !!!bar;
var foo = !!bar ? baz : bat;
var foo = Boolean(!!bar);
var foo = new Boolean(!!bar);
if (!!foo) {
// ...
}
if (Boolean(foo)) {
// ...
}
while (!!foo) {
// ...
}
do {
// ...
} while (Boolean(foo));
for (; !!foo; ) {
// ...
}
Examples of correct code for this rule:
/*eslint no-extra-boolean-cast: "error"*/
var foo = !!bar;
var foo = Boolean(bar);
function foo() {
return !!bar;
}
var foo = bar ? !!baz : !!bat;
Version
This rule was introduced in ESLint 0.4.0.