QJSPrimitiveValue Class
The QJSPrimitiveValue class operates on primitive types in JavaScript semantics. More...
| Header: | #include <QJSPrimitiveValue> |
| CMake: | find_package(Qt6 REQUIRED COMPONENTS Qml)target_link_libraries(mytarget PRIVATE Qt6::Qml) |
| qmake: | QT += qml |
| Since: | Qt 6.1 |
Public Types
| enum | Type { Undefined, Null, Boolean, Integer, Double, String } |
Detailed Description
QJSPrimitiveValue supports most of the primitive types defined in the ECMA-262 standard, in particular Undefined, Boolean, Number, and String. Additionally, you can store a JavaScript null in a QJSPrimitiveValue and as a special case of Number, you can store an integer value.
All those values are stored immediately, without interacting with the JavaScript heap. Therefore, you can pass QJSPrimitiveValues between different JavaScript engines. In contrast to QJSManagedValue, there is also no danger in destroying a QJSPrimitiveValue from a different thread than it was created in. On the flip side, QJSPrimitiveValue does not hold a reference to any JavaScript engine.
QJSPrimitiveValue implements the JavaScript arithmetic and comparison operators on the supported types in JavaScript semantics. Types are coerced like the JavaScript engine would coerce them if the operators were written in a JavaScript expression.
The JavaScript Symbol type is not supported as it is of very limited utility regarding arithmetic and comparison operators, the main purpose of QJSPrimitiveValue. In particular, it causes an exception whenever you try to coerce it to a number or a string, and we cannot throw exceptions without a JavaScript Engine.
Member Type Documentation
enum QJSPrimitiveValue::Type
This enum speicifies the types a QJSPrimitiveValue might contain.
| Constant | Value | Description |
|---|---|---|
QJSPrimitiveValue::Undefined | 0 | The JavaScript Undefined value. |
QJSPrimitiveValue::Null | 1 | The JavaScript null value. This is in fact not a separate JavaScript type but a special value of the Object type. As it is very common and storable without JavaScript engine, it is still supported. |
QJSPrimitiveValue::Boolean | 2 | A JavaScript Boolean value. |
QJSPrimitiveValue::Integer | 3 | An integer. This is a special case of the JavaScript Number type. JavaScript does not have an actual integer type, but the ECMA-262 standard contains rules on how to transform a Number in order to prepare it for certain operators that only make sense on integers, in particular the bit shift operators. QJSPrimitiveValue's Integer type represents the result of such a transformation. |
QJSPrimitiveValue::Double | 4 | A JavaScript Number value. |
QJSPrimitiveValue::String | 5 | A JavaScript String value. |