D 2011-12-11T16:33:56.166
L Dealing\swith\sJavaScript\sObjects
P bd5cd2de4b40197b1ba1c916733154148144064c
U murphy
W 6295
Dealing with JavaScript Objects
Value Conversions
| JavaScript Value | → | Scheme Value |
|---|
undefined | | (void) |
null | | '() |
| a boolean | | satisfies boolean? |
| a number | | satisfies number? |
| a string | | satisfies string? |
| a wrapper object | | the wrapped value |
| anything | | satisfies jso? |
| Scheme Value | → | JavaScript Value |
|---|
(void) | | undefined |
'() | | null |
satisfies boolean? | | a boolean |
satisfies number? | | a number |
satisfies string? | | a string |
satisfies symbol? | | a string |
satisfies jso? | | the wrapped object |
| anything | | a wrapper object |
If any JavaScript operation invoked from Scheme throws an error, a Scheme condition is raised with an equivalent error message.
If any Scheme operation invoked from JavaScript raises a condition, a JavaScript error is thrown with an equivalent error message.
Wrapper Records in Scheme
Complex JavaScript objects are not converted to Scheme values but rather encapsulted in a wrapper that allows various natural forms of access from Scheme. If the JavaScript object is a function, the resulting wrapper is callable as a procedure in addition to being accessible using the procedures described below.
(jso? VALUE) => BOOLEAN
Tests whether the VALUE is a wrapped JavaScript object.
(jso-new JSO ARGUMENT ...) => VALUE
Converts or unwraps the ARGUMENTs to JavaScript values, calls the JSO as a constructor with those arguments and returns the newly instantiated object converted or wrapped into a Scheme value.
(jso-apply JSO ARGUMENT ... REST) => VALUE
Converts or unwraps the ARGUMENTs (and the contents of REST) to JavaScript values, calls the JSO as a function with those arguments and returns the result converted or wrapped into a Scheme value.
(jso-exists? JSO KEY) => BOOLEAN
Checks whether the JSO has a property with a name obtained by stringifying KEY.
(jso-ref JSO KEY) => VALUE
Stringifies KEY, gets the property of JSO with the resulting name and returns the value converted or wrapped into a Scheme value.
(set! (jso-ref JSO KEY) VALUE) => VOID
(jso-set! JSO KEY VALUE) => VOID
Stringifies KEY, converts or unwraps VALUE to JavaScript and sets the property of JSO with the resulting name to the resulting value.
(jso-delete! JSO KEY)
Stringifies KEY, tries to delete the property of JSO with the resulting name and returns whether the operation was successful.
(:jso KEY JSO [(index INDEX)])
SRFI-42 generator syntax for the enumerable property names of a JavaScript object.
(jso-keys JSO) => LIST
Retrieves the enumerable property names of a JavaScript object as a list of strings.
Wrapper Objects in JavaScript
Complex Scheme values are not converted to JavaScript but rather encapsulated in a wrapper that allows various natural forms of access from JavaScript. If the Scheme value is a procedure, the resulting wrapper is callable as a function in addition to supporting the generic properties described below.
SCO.type => STRING
Returns a string describing the type of the wrapped Scheme value. Possible values are "hash-table", "vector", "pair", "procedure", the name of a SRFI-99 record type or the undefined value.
SCO.length => INTEGER
Returns the size of a hash table or the length of a vector. For other Scheme values the result is the undefined value.
SCO[STRING] => VALUE
SCO[STRING] = VALUE
delete SCO[STRING]
The string keys of a Scheme hash table are accessible as mutable, deletable properties.
SCO.car => VALUE
SCO.cdr => VALUE
SCO.c[ad]{2,5}r => VALUE
These direct and indirect properties of a pair are accessible as immutable properties.
SCO[NUMBER] => VALUE
The valid indices of a Scheme vector are accessible as mutable properties.
SCO[SYMBOL] => VALUE
SCO[SYMBOL] = VALUE
The fields of a transparent SRFI-99 record are accessible as (potentially mutable) properties.
SCO(ARGUMENT, ...) => VALUE
Converts or unwraps the ARGUMENTs to Scheme, applies the Scheme procedure wrapped by SCO to the resulting values and returns the result converted or wrapped into a JavaScript value.
String(SCO) => STRING
Stringifying a wrapper object produces the display representation of the Scheme value.
Utilities for DOM Objects
(xexpr->jso XEXPR DOCUMENT) => JSO
Converts the X-expression XEXPR into a DOM object using factory functions of the given DOCUMENT instance.
(jso->xexpr JSO [AT-ATTRIBUTES?]) => XEXPR
Converts the DOM object JSO into an X-expression. The optional
argument determines whether element attribute lists should be prefixed
with the symbol @.
Z 690749928b57885469c35dcfcf377063