Do You Remember Algebra From School?
Do you remember algebra from school? x=5, y=6, z=x+y
Do you remember that a letter (like x) could be used to hold a value (like 5), and that you could use the information above to calculate the value of z to be 11?
These letters are called variables, and variables can be used to hold values (x=5) or expressions (z=x+y).
A variable can have a short name, like x, or a more descriptive name, like carname.
- Variable names are case sensitive (y and Y are two different variables)
- Variable names must begin with a letter or the underscore character
A variable's value can change during the execution of a script. You can refer to a variable by its name to display or change its value.
This example will show you how
After the declaration shown above, the variables are empty (they have no values yet).
However, you can also assign values to the variables when you declare them:
After the execution of the statements above, the variable x will hold the value 5, and carname will hold the value Volvo.
Note: When you assign a text value to a variable, use quotes around the value.
You can have local variables with the same name in different functions, because local variables are only recognized by the function in which they are declared.
Local variables are destroyed when you exit the function.
Variables declared outside a function becomes GLOBAL, and all scripts and functions on the web page can access it.
Global variables are destroyed when you close the page.
If you declare a variable, without using "var", the variable always becomes GLOBAL.
If you assign values to variables that have not yet been declared, the variables will automatically be declared as global variables.
will declare the variables x and carname as global variables (if they don't already exist).