@putout/plugin-types
v5.1.0
Published
🐊Putout plugin adds ability to transform code related to types assertions
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@putout/plugin-types
🐊Putout plugin adds ability to help with transforming code related to types.
Install
npm i putout @putout/plugin-types -D
Rules
- ✅ apply-is-array;
- ✅ convert-typeof-to-is-type;
- ✅ declare;
- ✅ remove-double-negations;
- ✅ remove-useless-conversion;
- ✅ remove-useless-constructor;
- ✅ remove-useless-typeof;
Config
{
"rules": {
"types/declare": "on",
"types/convert-typeof-to-istype": "on",
"types/remove-useless-conversion": "on",
"types/remove-useless-constructor": "on",
"types/remove-double-negations": "on",
"types/remove-useless-typeof": "on",
"types/apply-is-array": "on"
}
}
declare
Based on @putout/operator-declare
.
Supported assertions:
isString
;isEmptyString
;isNumber
;isFn
;isBool
;isObject
;isUndefined
;isSymbol
;isNull
;isBigInt
;isArray
;isEmptyArray
;
❌ Example of incorrect code
isString('hello');
✅ Example of correct code
const isString = (a) => typeof a === 'string';
isString('hello');
When you want to skip some declaration use dismiss
:
{
"rules": {
"types/declare": ["on", {
"dismiss": ["isString"]
}]
}
}
convert-typeof-to-is-type
The
typeof
operator returns a string indicating the type of the unevaluated operand.(c) MDN
❌ Example of incorrect code
if (typeof a === 'boolean')
return x;
✅ Example of correct code
const isBool = (a) => typeof a === 'boolean';
if (isBool(a))
return x;
remove-useless-conversion
❌ Example of incorrect code
const a = !![1].includes(1);
const b = Boolean([1].includes(1));
✅ Example of correct code
const a = [1].includes(1);
remove-useless-constructor
Wrapper classes have surprising behaviour, such as
new Boolean(false)
evaluating totrue
.
🐊Putout plugin adds ability to remove useless constructor
. Use with new/remove-useless
.
❌ Example of incorrect code
const s = String('hello');
const b = Boolean(false);
const n = Number(5);
✅ Example of correct code
const s = 'hello';
const b = false;
const n = 5;
remove-double-negations
It is possible to use a couple of NOT operators (
!!
) in series to explicitly force the conversion of any value to the corresponding boolean primitive. The conversion is based on the "truthyness" or "falsyness" of the value.The same conversion can be done through the
Boolean
function.(c) MDN
❌ Example of incorrect code
if (!!a)
console.log('hi');
✅ Example of correct code
if (a)
console.log('hi');
remove-useless-typeof
The
typeof
operator returns a string indicating the type of the unevaluated operand.(c) MDN
❌ Example of incorrect code
typeof typeof 'hello';
✅ Example of correct code
typeof 'hello';
apply-is-array
The
Array.isArray()
method determines whether the passed value is anArray
. When checking forArray
instance,Array.isArray()
is preferred overinstanceof
because it works throughiframes
.
❌ Example of incorrect code
x instanceof Array;
✅ Example of correct code
const {isArray} = Array;
isArray(x);
In case of using inline
option:
{
"rules": {
"types/apply-is-array": ["on", {
"inline": true
}]
}
}
Array.isArray
will be inlined:
Array.isArray(x);
License
MIT
Comparison
Linter | Rule | Fix
--------|-------|------------|
🐊 Putout | types
| ✅
⏣ ESLint | no-implicit-coercion
| ✅
License
MIT