Disallow shorthand type conversions
Some problems reported by this rule are automatically fixable by the --fix
command line option
In JavaScript, there are a lot of different ways to convert value types. Some of them might be hard to read and understand.
Such as:
var b = !!foo;
var b = ~foo.indexOf(".");
var n = +foo;
var n = 1 * foo;
var s = "" + foo;
foo += ``;
Those can be replaced with the following code:
var b = Boolean(foo);
var b = foo.indexOf(".") !== -1;
var n = Number(foo);
var n = Number(foo);
var s = String(foo);
foo = String(foo);
This rule is aimed to flag shorter notations for the type conversion, then suggest a more self-explanatory notation.
This rule has three main options and one override option to allow some coercions as required.
"boolean"
(true
by default) - When this is true
, this rule warns shorter type conversions for boolean
type."number"
(true
by default) - When this is true
, this rule warns shorter type conversions for number
type."string"
(true
by default) - When this is true
, this rule warns shorter type conversions for string
type."disallowTemplateShorthand"
(false
by default) - When this is true
, this rule warns string
type conversions using ${expression}
form."allow"
(empty
by default) - Each entry in this array can be one of ~
, !!
, +
or *
that are to be allowed.Note that operator +
in allow
list would allow +foo
(number coercion) as well as "" + foo
(string coercion).
Examples of incorrect code for the default { "boolean": true }
option:
Examples of correct code for the default { "boolean": true }
option:
Examples of incorrect code for the default { "number": true }
option:
Examples of correct code for the default { "number": true }
option:
Examples of incorrect code for the default { "string": true }
option:
Examples of correct code for the default { "string": true }
option:
This option is not affected by the string
option.
Examples of incorrect code for the { "disallowTemplateShorthand": true }
option:
Examples of correct code for the { "disallowTemplateShorthand": true }
option:
Examples of correct code for the default { "disallowTemplateShorthand": false }
option:
Using allow
list, we can override and allow specific operators.
Examples of correct code for the sample { "allow": ["!!", "~"] }
option:
If you don’t want to be notified about shorter notations for the type conversion, you can safely disable this rule.
This rule was introduced in ESLint v1.0.0-rc-2.
© OpenJS Foundation and other contributors
Licensed under the MIT License.
https://eslint.org/docs/latest/rules/no-implicit-coercion