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AppleEvent to JavaScript Value Conversion
The MacOS.AEApp, MacOS.AEClass and MacOS.AEColl objects perform JavaScript to AppleEvent conversions when sending AppleEvents to another Macintosh Application. AppleEvent to JavaScript conversions are performed on the result of an AppleEvent.
JavaScript To AppleEvent Value Conversions
| JavaScript Value | AppleEvent Value |
| string | string |
| integer | long integer |
| float | long float |
| boolean | boolean |
| array | list |
| object | record (see notes below) |
| MacOS.FileSpec | file specification |
| MacOS.AEDesc | the AEDesc value |
| undefined | undefined |
| null | missing value |
AppleEvent To JavaScript Value Conversions
AppleEvents have a greater number of ways of expressing values than does JavaScript. Because of this, JavaScript OSA AppleEvent to JavaScript conversion process maps several AppleEvent data types onto a single JavaScript data type.
| AppleEvent Value | JavaScript Value |
| string international string styled string unicode string P-string C-string |
string |
| long integer short integer magnitude |
integer |
| long float short float |
float |
| boolean true false |
Boolean |
| file specification alias |
MacOS.FileSpec |
| list | array |
| record | object (see notes below) |
| undefined | undefined |
| missing value | null |
| anything else | MacOS.AEDesc |
JavaScript Object/AppleEvent Record Conversions
An AppleEvent record is a collection of properties, much as a JavaScript Object is. The difference is that there may be two kinds of property in an AppleEvent record: keyed properties and user properties.
A keyed property is identified by a unique 4-character key that usually maps to a property definition in an application dictionary. If the AppleEvent/JavaScript conversion is performed by a method or property of the MacOS.AEApp, MacOS.AEClass or MacOS.AEColl objects, keyed properties in JavaScript may be referred to using the name defined for the key in the target application's dictionary. If the conversion is happening in any other context, the JavaScript name given to the property is "ae_xxxx" where xxxx is the property's four-character.
NOTE: if a property key contains characters that cannot appear in a JavaScript identifier, use JavaScript's array syntax to access the property (e.g.: aVar["ae_----"]).
A user property is a named property where the name is an arbitrary string of any length (there is a generally accepted 255 character limit). User properties map directly to properties of JavaScript objects.