11.7. WMLScript typeof Operator - Finding Data Types of Variables

As mentioned previously in the "WMLScript Data Types" section of this WMLScript tutorial, there is only one type of variable in WMLScript, which is var. A variable can contain a value of any of the five primitive data types -- Boolean, integer, float, string and invalid. If you want to determine the data type of the value stored in a variable, you can make use of the typeof operator. The typeof operator returns an integer that indicates the data type of a value.


WMLScript data type

Return value of the typeof operator

Integer

0

Float

1

String

2

Boolean

3

Invalid

4


The following WMLScript example demonstrates how to use the typeof operator to find the data type of the value stored in a variable:


var number1 = 100;
var number2 = 1.11;
var x = typeof number1;
var y = typeof number2;


After the execution of the above script, the x variable contains the value 0 (indicates that an integer is stored in the number1 variable) while the y variable contains the value 1 (indicates that a floating-point number is stored in the number2 variable).

The operand of the typeof operator does not have to be a variable. For example:


var x = typeof (100 / 0);
var y = typeof (10 / 3);
var z = typeof "WMLScript Tutorial";


After executing the above script, x contains 4 (invalid type), y contains 1 (float type) and z contains 2 (string type).


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