JavaScript Operators

written by: George Freedrich; article published: year 2008, month 12;

In: Root » Computers and technology » AJAX and JavaScript

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Operators can be placed into three categories-binary, unary, and ternary. Binary operators, most commonly associated with the concept of operator, take two (binary) expressions and combine them into a third complex or compound expression. However, a single expression can have several binary operators. For example, the following variable declaration uses multiple binary operators to define the variable:

var calcAdd = (total / n ) + 73

The divide (/) operator and the plus (+) operator are binary operators. The first combination occurs when the variable total is divided by the variable n. The two variables become a single value. That single value resulting from total divided by n is then added to the literal numeric value of 73, creating yet another value. The equals sign (=) places the combined value of the operands into the variable calcAdd.

Unary operators work on a single variable or literal. All negative numbers are assigned using a unary operator. For example, the following little script uses a unary operator to create a variable with a negative value:

<html> 
<head> 
<script language="JavaScript"> 
var posNum=85; 
var negNum= -posNum; 
document.write(negNum); 
</script> 
</head> 
<body bgcolor="honeydew"> 
</body> 
</html>

The return of the script is -85 because the minus (-) unary operator defined the variable negNum as the negation of the variable posNum. Other common unary operators include increment or decrement operators (++ and - -) seen in counter variables.

Finally, ternary operators combine three expressions into one. Most commonly used to create a shorthand expression for conditional statements, the only ternary operator in JavaScript is ? :. For example, this conditional statement:

if(alpha == beta) {
      gamma=56; 
      } else {
      gamma=57; 
      }

can be written with a ternary operator as follows:

alpha == beta ? gamma=56 : gamma=57;

The following little script shows how both methods arrive at the same conclusion:

<html> 
<head> 
<script language="JavaScript"> 
var alpha=20, beta=30, gamma=0, lambda=0; 
if (alpha==beta) {
var gamma=56; 
} else {
gamma=57; 
} 
//Same set of conditions using ternary operator 
alpha==beta ? lambda=56 : lambda=57; 
document.write("Conditional results:" + gamma + "<p>" + "Ternary conditional:" + lambda); 
</script> 
</head> 
<body bgcolor="oldlace"> 
</body> 
</html>

The three elements that the ?: operator brought together in the example are (alpha==beta), (lambda=56), and (lambda=57). Note also how the comma (,) operator is used in the script to separate the definitions of the variables alpha, beta, gamma, and lambda at the beginning of the script.

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