Operators

The operators of JSX are the same to those in JavaScript (ECMA-262 3rd edition) except for the following changes.

• types of the operands accepted by the operators are more restrictive
• logical operators (&& ||) return boolean
• binary ?: operator has been introduced (to cover the use of || in JavaScript to return non-boolean values)
• introduction of the as operator
• delete is a statement instead of an operator
• a wrapper object (Boolean, Number, String) cannot become a left-hand-side expression

The table below lists the operators supported by JSX.

List of Operators by Precedence

Operator	Returned Type	Operand Type(s)	Note
(x)	typeof x		grouping operator
(...)	returned type of the called function		function call
x.property	typeof x.property	x:Object
array[index]	Nullable.<T>	array: Array.<T>, index: number
map[key]	Nullable.<T>	map: Map.<T>, key: string
x++	typeof x	number or int
x--	typeof x	number or int
x instanceof y	boolean	x: Object, y: Class, Interface, Mixin
x as type	type		cast operator
x as __noconvert__ type	type		cast operator (without run-time type check)
++x	typeof x	number or int
--x	typeof x	number or int
+x	typeof x	number or int
-x	typeof x	number or int
~x	int	number or int
! x	boolean	any
typeof x	boolean	variant
x * y	number or int	number, int, Number	int is returned if both operands are int
x / y	number or int	number, int, Number	int is returned if both operands are int
x % y	number	number, int, Number
x + y	string	string or String
x + y	number or int	number, int, Number	int is returned if both operands are int
x - y	number or int	number, int, Number	int is returned if both operands are int
x << y	int	number, int, Number
x >> y	int	number, int, Number
x >>> y	int	number, int, Number
x < y	boolean	number, int, string, Number, String
x <= y	boolean	number, int, string, Number, String
x > y	boolean	number, int, string, Number, String
x >= y	boolean	number, int, string, Number, String
x in y	boolean	x: string, y: Map.<T>
x == y	boolean	boolean, number, int, string, Object
x != y	boolean	boolean, number, int, string, Object
x & y	int	number, int, Number
x ^ y	int	number, int, Number
x | y	int	number, int, Number
x && y	boolean	any
x || y	boolean	any
x ? y : z	typeof y		returned types of y and z should be equal
x ?: y	typeof x		returned types of x and y should be equal
x = y	typeof x		type of y should be convertible to type of x
x op= y	typeof x	same as op, except that x cannot be a wrapper object	op can be any of: * / % + - << >> >>> & ^ |
x, y	typeof y

As Operator

The as operator is used for: conversion between primitive types (including Nullable and variant), down-casting of object types.

The conversion rules between primitive types are defined as follows. If the source type is a Nullable type and if the value is null, a run-time exception is raised under debug builds. The behavior is unspecified for release builds.

The result of conversion from a variant type depends on the result of the typeof operator applied to the variant.

Down-casting of an object type returns a reference to the casted object if successful, otherwise null.

Conversion between Primitive Types using the As Operator

Source Type	Destination Type	Result
boolean	number	0 if false, 1 if true
boolean	int	same as above
boolean	string	"false" if false, "true" if true
number	boolean	false if 0 or NaN, otherwise true
number	int	fractional part is removed, becomes 0 if NaN, may get rounded to between -231 and 231-1
number	string	converted to string representation
int	boolean	false if 0, otherwise true
int	number	converted to number of same value
int	string	converted to string representation
string	boolean	false if the string is empty, otherwise true
string	number	0 if the string is empty, a number if the string can be parsed as a string, otherwise NaN
string	int	equivalent to: as number as int

Conversion from Variant using the As Operator

Result of typeof(variant)	Destination Type	Result
"undefined"	boolean	false
"undefined"	number	NaN
"undefined"	int	0
"undefined"	string	"undefined"
"null"	boolean	false
"null"	number	0
"null"	int	0
"null"	string	"null"
"boolean"	any primitive type	equivalent to the result of: boolean as type
"number"	any primitive type	equivalent to the result of: number as type
"string"	any primitive type	equivalent to the result of: string as type
"object"	any primitive type	depends on the actual type of the value
"object"	any object type	reference to the object if the value is an object of the specified type, otherwise null