[−][src]Enum boa::syntax::ast::op::UnaryOp
A unary operator is one that takes a single operand/argument and performs an operation.
A unary operation is an operation with only one operand. This operand comes either before or after the operator. Unary operators are more efficient than standard JavaScript function calls.
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Variants
The increment operator increments (adds one to) its operand and returns a value.
Syntax: ++x
This operator increments and returns the value after incrementing.
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The increment operator increments (adds one to) its operand and returns a value.
Syntax: x++
This operator increments and returns the value before incrementing.
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The decrement operator decrements (subtracts one from) its operand and returns a value.
Syntax: --x
This operator decrements and returns the value before decrementing.
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The decrement operator decrements (subtracts one from) its operand and returns a value.
Syntax: x--
This operator decrements the operand and returns the value after decrementing.
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The unary negation operator precedes its operand and negates it.
Syntax: -x
Converts non-numbers data types to numbers like unary plus, however, it performs an additional operation, negation.
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The unary plus operator attempts to convert the operand into a number, if it isn't already.
Syntax: +x
Although unary negation (-
) also can convert non-numbers, unary plus is the fastest and preferred
way of converting something into a number, because it does not perform any other operations on the number.
It can convert string
representations of integers and floats, as well as the non-string values true
, false
, and null
.
More information:
Returns false
if its single operand can be converted to true
; otherwise, returns true
.
Syntax: !x
Boolean values simply get inverted: !true === false
and !false === true
.
Non-boolean values get converted to boolean values first, then are negated.
This means that it is possible to use a couple of NOT operators in series to explicitly
force the conversion of any value to the corresponding boolean primitive.
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Performs the NOT operator on each bit.
Syntax: ~x
NOT a
yields the inverted value (or one's complement) of a
.
Bitwise NOTing any number x yields -(x + 1). For example, ~-5 yields 4.
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The typeof
operator returns a string indicating the type of the unevaluated operand.
Syntax: typeof x
or typeof(x)
The typeof
is a JavaScript keyword that will return the type of a variable when you call it.
You can use this to validate function parameters or check if variables are defined.
There are other uses as well.
More information:
The JavaScript delete
operator removes a property from an object.
Syntax: delete x
Unlike what common belief suggests, the delete operator has nothing to do with directly freeing memory. Memory management is done indirectly via breaking references. If no more references to the same property are held, it is eventually released automatically.
The delete
operator returns true
for all cases except when the property is an
own
non-configurable
property, in which case, false
is returned in non-strict mode.
More information:
The void
operator evaluates the given expression
and then returns undefined
.
Syntax: void x
This operator allows evaluating expressions that produce a value into places where an
expression that evaluates to undefined
is desired.
The void
operator is often used merely to obtain the undefined
primitive value, usually using void(0)
(which is equivalent to void 0
). In these cases, the global variable undefined can be used.
When using an immediately-invoked function expression,
void
can be used to force the function keyword to be treated as an expression instead of a declaration.
More information:
Trait Implementations
impl Clone for UnaryOp
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impl Copy for UnaryOp
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impl Debug for UnaryOp
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impl Display for UnaryOp
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impl Finalize for UnaryOp
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impl PartialEq<UnaryOp> for UnaryOp
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impl StructuralPartialEq for UnaryOp
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impl Trace for UnaryOp
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Auto Trait Implementations
impl RefUnwindSafe for UnaryOp
impl Send for UnaryOp
impl Sync for UnaryOp
impl Unpin for UnaryOp
impl UnwindSafe for UnaryOp
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
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fn clone_into(&self, target: &mut T)
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impl<T> ToString for T where
T: Display + ?Sized,
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T: Display + ?Sized,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<V, T> VZip<V> for T where
V: MultiLane<T>,
V: MultiLane<T>,