JavaScript.Extras.Cast

Documentation

class ToJS a where

This provides a consistent way to convert to JSVal, with different semantics for Char. In the Char's instance of ToJS, it converts to a string instead of integer - IMHO this is less surprising.

The other reason for this class is while GHCJS base provide both IsJSVal and PToJSVal to convert to jsval, some types are instances of one or the other class. This means you can't use the "Maybe a" instance of PToJSVal if it contains IsISJVal but not pToJSVal.

Methods

toJS :: a -> JSVal

This is a pure conversion, so instances must be able to convert the same or equivalent JSVal each time.

toJS :: IsJSVal a => a -> JSVal

This is a pure conversion, so instances must be able to convert the same or equivalent JSVal each time.

Instances

ToJS Bool

Defined in JavaScript.Extras.Cast

Methods

toJS :: Bool -> JSVal

ToJS Char

Char instance converts to string

Defined in JavaScript.Extras.Cast

Methods

toJS :: Char -> JSVal

ToJS Double

Defined in JavaScript.Extras.Cast

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toJS :: Double -> JSVal

ToJS Float

Defined in JavaScript.Extras.Cast

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toJS :: Float -> JSVal

ToJS Int

Defined in JavaScript.Extras.Cast

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toJS :: Int -> JSVal

ToJS Int8

Defined in JavaScript.Extras.Cast

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toJS :: Int8 -> JSVal

ToJS Int16

Defined in JavaScript.Extras.Cast

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toJS :: Int16 -> JSVal

ToJS Int32

Defined in JavaScript.Extras.Cast

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toJS :: Int32 -> JSVal

ToJS Word

Defined in JavaScript.Extras.Cast

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toJS :: Word -> JSVal

ToJS Word8

Defined in JavaScript.Extras.Cast

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toJS :: Word8 -> JSVal

ToJS Word16

Defined in JavaScript.Extras.Cast

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toJS :: Word16 -> JSVal

ToJS Word32

Defined in JavaScript.Extras.Cast

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toJS :: Word32 -> JSVal

ToJS String

Defined in JavaScript.Extras.Cast

Methods

toJS :: String -> JSVal

ToJS Text

Defined in JavaScript.Extras.Cast

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toJS :: Text -> JSVal

ToJS Object

Defined in JavaScript.Extras.Cast

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toJS :: Object -> JSVal

ToJS JSString

Defined in JavaScript.Extras.Cast

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toJS :: JSString -> JSVal

ToJS JSVal

Defined in JavaScript.Extras.Cast

Methods

toJS :: JSVal -> JSVal

ToJS JSRep

Defined in JavaScript.Extras.JSRep

Methods

toJS :: JSRep -> JSVal

ToJS a => ToJS (Maybe a)

Defined in JavaScript.Extras.Cast

Methods

toJS :: Maybe a -> JSVal

ToJS (Nullable a)

Defined in JavaScript.Extras.Cast

Methods

toJS :: Nullable a -> JSVal

ToJS (Callback a)

Defined in JavaScript.Extras.Cast

Methods

toJS :: Callback a -> JSVal

ToJS (Export a)

Defined in JavaScript.Extras.Cast

Methods

toJS :: Export a -> JSVal

ToJS (SomeJSArray m)

Defined in JavaScript.Extras.Cast

Methods

toJS :: SomeJSArray m -> JSVal

class FromJS a where

This provides a consistent way to safely convert from JSVal. The semantics is that if the return value is a Just, then the JSVal is not a null value. Also, Nothing is also returned for values out of range. They are not silently truncated. (Except for Float where there may be loss of precision) during conversion.

The reason for this class is because GHCJS.Marshal.fromJSVal and GHCJS.Marshal.pFromJSVal are not safe to use as it assumes that the JSVal are of the correct type and not null. (https:/github.comghcjsghcjs-baseissues/87). The safe way to convert from JSVal is to use JavaScript.Cast or to use the 'Maybe a' instance of FromJSVal, ie fromJSVal :: JSVal -> IO (Maybe (Maybe a)), which is a bit more awkward to use, and requires IO. Also, Javascript.Cast doesn't have much instances, and it hardcodes the instance detection method to javascript isinstance which is not sufficient for complex types (https:/github.comghcjsghcjs-baseissues/86).

It is actually safe to convert from JSVal without IO because every JSVal is a copy of a value or reference. The copy never change, so the conversion will always convert to the same result/object every time.

Minimal complete definition

fromJS

Methods

fromJS :: JSVal -> Maybe a

Instances

FromJS Bool

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe Bool

FromJS Char

This will only succeed on a single character string

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe Char

FromJS Double

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe Double

FromJS Float

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe Float

FromJS Int

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe Int

FromJS Int8

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe Int8

FromJS Int16

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe Int16

FromJS Int32

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe Int32

FromJS Word

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe Word

FromJS Word8

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe Word8

FromJS Word16

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe Word16

FromJS Word32

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe Word32

FromJS String

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe String

FromJS Text

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe Text

FromJS Object

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe Object

FromJS JSString

Defined in JavaScript.Extras.Cast

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fromJS :: JSVal -> Maybe JSString

FromJS JSVal

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe JSVal

FromJS JSRep

Defined in JavaScript.Extras.JSRep

Methods

fromJS :: JSVal -> Maybe JSRep

FromJS (SomeJSArray m)

Defined in JavaScript.Extras.Cast

Methods

fromJS :: JSVal -> Maybe (SomeJSArray m)