| Null type has only one value, null. The null value means ‘no data’ or this variable do not have any useful data. |
| Undefined type has one value, undefined, undefined means nothing is stored in this variable. Undefined is not even null. |
| Initializing null type variable |
| var food = null |
| var is JavaScript keyword, food is a variable name, null is value assigned to food variable. |
| In the example given below we have used keyword document.write (message ) which is used to printthe message or variable value given with it. |
| Example 1 |
| <html>
<head> </head> <body> <script type=”text/JavaScript”> var food=null document.write(“food is : “+food); </script > </body> </html> |
| Understanding the program |
| food is a variable of null type having no type of values or data. |
| output of this program |
| food is : null |
| click here to view result of this program in browser |
| Knowing undefined type variable |
| var food ; |
| var is JavaScript keyword, food is a variable name, no value is assigned to variable food. |
| In the example given below we have used keyword document.write (message ) which is used to print the message or variable value given with it. |
| Example 2 |
| <html>
<head> </head> <body> <script type=”text/javascript”> var food; document.write(“food is : “+food); </script > </body> </html> |
| Understanding the program |
| food is a variable of undefined type , because nothing is defined to it . |
| Output of this program |
| food is : undefined |