QJSValue Class

The QJSValue class holds a value of a JavaScript engine. More…

List of all members, including inherited members

Public Types

Public Functions

Detailed Description

A QJSValue is a primitive (undefined, null, a boolean, a number or a string) or a reference to an object of a QJSEngine. Copies refer to the same object, and keep it alive.

QJSValue point = engine.newObject();
point.setProperty("x", 3);
point.setProperty("y", 4);
QJSValue length = engine.evaluate("(function(p) { return Math.hypot(p.x, p.y); })");
qDebug() << length.call({point}).toNumber();   // 5

Values made without an engine, such as QJSValue(42), are primitives; they can be passed to any engine. Objects belong to the engine that made them; after the engine is destroyed they read as undefined.

Calling a function that throws returns the error: check isError(). Arguments are passed as a QJSValueList, a QList of QJSValue.

See also QJSEngine.

Differences from Qt

Member Type Documentation

enum QJSValue::ErrorType

The type of an error object.

enum QJSValue::ObjectConversionBehavior

How toVariant() converts objects.

enum QJSValue::SpecialValue

Member Function Documentation

QJSValue::QJSValue(SpecialValue value = UndefinedValue)

Constructs value: undefined or null.

QJSValue::QJSValue(bool value)

Constructs the boolean value.

QJSValue::QJSValue(int value)

Constructs the number value.

QJSValue::QJSValue(uint value)

Constructs the number value.

QJSValue::QJSValue(double value)

Constructs the number value.

QJSValue::QJSValue(const QString &value)

Constructs the string value.

QJSValue::QJSValue(QLatin1String value)

Constructs the string value.

QJSValue::QJSValue(const char *str)

Constructs the string str, read as UTF-8.

QJSValue::QJSValue(const QJSValue &other)

Constructs a copy of other, which refers to the same object.

QJSValue::QJSValue(QJSValue &&other)

Constructs a value by moving other.

QJSValue::~QJSValue()

Destroys the value. The object it refers to may be collected once nothing else refers to it.

QJSValue QJSValue::call(const QJSValueList &args = QJSValueList()) const

Calls the function with args and this undefined, and returns its result, or the error it throws.

QJSValue QJSValue::callAsConstructor(const QJSValueList &args = QJSValueList()) const

Calls the function as a constructor, as new does, with args, and returns the new object, or the error it throws.

QJSValue QJSValue::callWithInstance(const QJSValue &instance, const QJSValueList &args = QJSValueList()) const

Calls the function with args and instance as this, and returns its result, or the error it throws.

bool QJSValue::deleteProperty(const QString &name)

Deletes the property name of the object. Returns true on success.

bool QJSValue::equals(const QJSValue &other) const

Returns true if the value equals other with JavaScript's == operator; otherwise returns false.

ErrorType QJSValue::errorType() const

Returns the type of the error, or NoError if the value is not an error.

bool QJSValue::hasOwnProperty(const QString &name) const

Returns true if the object itself has the property name; otherwise returns false.

bool QJSValue::hasProperty(const QString &name) const

Returns true if the object or its prototypes have the property name; otherwise returns false.

bool QJSValue::isArray() const

Returns true if the value is an array; otherwise returns false.

bool QJSValue::isBool() const

Returns true if the value is a boolean; otherwise returns false.

bool QJSValue::isCallable() const

Returns true if the value is a function; otherwise returns false.

bool QJSValue::isDate() const

Returns true if the value is a Date; otherwise returns false.

bool QJSValue::isError() const

Returns true if the value is an error; otherwise returns false.

bool QJSValue::isNull() const

Returns true if the value is null; otherwise returns false.

bool QJSValue::isNumber() const

Returns true if the value is a number; otherwise returns false.

bool QJSValue::isObject() const

Returns true if the value is an object, functions and arrays included; otherwise returns false.

bool QJSValue::isQObject() const

Returns true if the value is a QObject; otherwise returns false.

See also toQObject().

bool QJSValue::isRegExp() const

Returns true if the value is a RegExp; otherwise returns false.

bool QJSValue::isString() const

Returns true if the value is a string; otherwise returns false.

bool QJSValue::isUndefined() const

Returns true if the value is undefined; otherwise returns false.

bool QJSValue::isUrl() const

Returns true if the value is a URL; otherwise returns false. URLs are strings in Nt, so this is always false.

bool QJSValue::isVariant() const

Returns true if the value holds a C++ value that has no JavaScript form; otherwise returns false.

QJSValue & QJSValue::operator=(const QJSValue &other)

Makes this value refer to what other refers to.

QJSValue & QJSValue::operator=(QJSValue &&other)

Moves other into this value.

QJSValue QJSValue::property(const QString &name) const

Returns the property name of the object, or undefined. A getter that throws gives the error.

QJSValue QJSValue::property(quint32 arrayIndex) const

This is an overloaded function.

Returns the element arrayIndex of the object.

QJSValue QJSValue::prototype() const

Returns the prototype of the object, or null.

void QJSValue::setProperty(const QString &name, const QJSValue &value)

Sets the property name of the object to value.

void QJSValue::setProperty(quint32 arrayIndex, const QJSValue &value)

This is an overloaded function.

Sets the element arrayIndex of the object to value.

void QJSValue::setPrototype(const QJSValue &prototype)

Sets the prototype of the object to prototype, an object or null. A prototype that would make a cycle is ignored.

bool QJSValue::strictlyEquals(const QJSValue &other) const

Returns true if the value equals other with JavaScript's === operator; otherwise returns false.

void QJSValue::swap(QJSValue &other)

Swaps this value with other.

bool QJSValue::toBool() const

Returns the value converted to a boolean, as JavaScript's Boolean(value) does.

QDateTime QJSValue::toDateTime() const

Returns the date the value holds, or an invalid QDateTime if it is not a Date.

qint32 QJSValue::toInt() const

Returns the value converted to a 32-bit integer, as JavaScript's value | 0 does.

double QJSValue::toNumber() const

Returns the value converted to a number, as JavaScript's Number(value) does.

QObject * QJSValue::toQObject() const

Returns the QObject the value refers to, or nullptr if it is not a QObject or the object was deleted.

QString QJSValue::toString() const

Returns the value converted to a string, as JavaScript's String(value) does. An error while converting gives the text of the error.

quint32 QJSValue::toUInt() const

Returns the value converted to a 32-bit unsigned integer, as JavaScript's value >>> 0 does.

QVariant QJSValue::toVariant() const

Returns the value as a QVariant: booleans, numbers (as double) and strings as such, arrays as QVariantList, dates as QDateTime, QObjects as QObject *, other objects as QVariantMap, and null as a QVariant holding nullptr.

QVariant QJSValue::toVariant(ObjectConversionBehavior behavior) const

This is an overloaded function.

Returns the value as a QVariant; behavior is not used.