Expressions and Operators

Expressions and operators in Ejscript and ECMAScript follow closely their cousins in C and Java. Users familiar with these languages should feel right at home.

Expressions are combinations of variables and operators that evaluate to a single value. Expressions can be used as the right hand side of an assignment, as function arguments, and in return statements.

Operator Summary

The following table summarizes the operators available in Ejscript. For a complete specification, please consult the ECMA-262 specification.

Operator Operands Description
*  /  % Numbers Multiply, divide, modulo
+ Numbers, Strings Add numbers, catenate strings
- Numbers Subtract numbers
! Boolean Unary not
++ Numbers Pre/Post-increment number
-- Numbers Pre/Post-decrement number
<< Integers Left shift
>> Integers Right shift
==  != All Compare if equal, not equal
===  !== All Strict equality, inequality. Object references must equal.
<  <= Numbers, Strings Compare if less than, less than or equal
>  >= Numbers, Strings Compare if greater than, greater than or equal
& Numbers Bitwise AND
| Numbers Bitwise OR
&& Booleans Logical AND
|| Booleans Logical OR
. object.property Property access
[] array[integer]
array[string]
Array, Object, ByteArray element access
() function(any, ...) Function call
cast Any Cast the operand to the required type
is Any Test if the operand is the required type
in Any Test if name is a property of the target object
is instanceof like Any Test if the operand is of the required type

The following operators can also be combined with assignment to provide a compound operator: * / % + - ! << >> & | && and ||. For example:

x += 2

Ejscript uses a type-less VM where the types themselves implement the operators. Users can define new native types which implement any of the operators on their native type.

Operator Precedence

When expressions are evaluated, the operands bind to the operators depending on the precedence of the operators.

The following table lists the operators in order of highest to lowest precedence. Operators of the same precedence share the same row in the table:

Operator
.  []  ()  new
++  --  -  +  delete
*  /  %
+  -
<<  >>
<  <=  >  >= cast in instanceof in is like
==  !=
&&
||
=
,

For example, the expression: a = x + y * z is equivalent to a = x + (y * z).

© Embedthis Software, 2003-2015. All rights reserved.