Chapter 2 The DynaScript Language

Operators

This section describes the operators available in scripts.

Ternary, binary and unary operators

Operators act on one or more expressions called operands. Operators can be either ternary, binary or unary: ternary operators act on three expressions, binary operators act on two expressions, and unary operators act on one.

For example, the addition operator is a binary operator, so the following is a valid expression:

x + y ;

The increment operator (which adds one to a number) is a unary operator, so the following is a valid expression:

x++ ;

Arithmetic operators

The following arithmetic operators are provided:

Operator	Description	Binary or unary
+	addition	binary
-	subtraction	binary
*	multiplication	binary
/	division	binary
%	modulo	binary
++	increment	unary
--	decrement	unary
-	negation	unary

Notes

Comparison operators can also operate on numbers, but the result is a Boolean value.
The increment and decrement operators can be used either before or after the operand: both of the following are valid statements:
```
x++
++x
```
When the operator precedes the operand, the operand is decremented before the expression is evaluated; if the operator follows the operand, the operand is decremented after the expression is evaluated. The following statements illustrate the difference:
```
x = 56 ;
y = x-- ;  // Sets y to 56 and decrements x to 55
y = --x ;  // Decrements x to 55 and sets y to 55
```

Conditional operator

The following conditional operator is provided:

Operator	Description
?	Conditional

The ? operator is ternary, meaning that it acts on three expressions.

The ? operator evaluates to one of two values, based on a condition. An example of the ? operator is as follows:

(grade == "pass") ? "Excellent" : "Try again";

String operators

The following string operators are provided:

Operator	Description
+	Concatenation
+=	Concatenation with assignment

Comparison operators can also operate on strings, but the result is a Boolean value.

Comparison operators

The following comparison operators are provided:

Operator	Description
= =	Equal to
>	Greater than
<	Less than
>=	Greater than or equal to
<=	Less than or equal to
<>	Not equal to
!=	Not equal to

These operators can act on numbers or strings, and return a Boolean (logical) value of true or false .

Boolean operators

Boolean operators operate on Boolean (logical) expressions. The following Boolean operators are provided:

Operator	Name	Description
&&	And	Returns true if both expression are true, false otherwise.
\|\|	Or	Returns true if either expression is true.
!	Not	Returns true if the expression is false, and false if the expression is true.

Bitwise operators

Bitwise operators treat their operands as a set of bits (zeros and ones), rather than as decimal, hexadecimal, or octal numbers. Bitwise operators perform their operations on such binary representations, but they return standard numerical values.

The following bitwise operators are provided:

Operator	Name	Description
&	AND	Returns a one if both operands are ones.
\|	OR	Returns a one if either operand is one.
^	XOR	Returns a one if one but not both operands are one.
<<	Left shift	Shifts the first operand the specified number of bits to the left. Excess bits shifted off to the left are discarded. Zero bits are shifted in from the right.
>>	Sign-propagating Right shift	Shifts the first operand the specified number of bits to the right. Excess bits shifted off to the right are discarded. Copies of the leftmost bit are shifted in from the left.
>>>	Zero-fill right shift	Shifts the first operand the specified number of bits to the right. Excess bits shifted off to the right are discarded. Zero bits are shifted in from the left.

Delete operator

The delete operator may be used to delete a property from an object or to delete an element from an array. For example

delete x

Returns true if deletion is successful, false otherwise.

Void operator

The void operator may be used to prevent an expression from returning a value. For example

void addVar

The void operator will evaluate its expression and then returned undefined .

Typeof operator

The typeof operator may be used to return the datatype of an expression. For example

document.writeln( typeof(addVar) );

The typeof operator returns a string that can be one of number, string, Boolean, object, function or undefined.