= is used to assign values.
+ is used to add values.
The assignment operator = is used to assign values to JavaScript variables.
The arithmetic operator + is used to add values together.
| y=5; z=2; x=y+z; |
The value of x, after the execution of the statements above is 7.
As with algebra, you can do arithmetic operations with JavaScript variables:
y=x-5;If you redeclare a JavaScript variable, it will not lose its original value.
| var x=5; var x; |
After the execution of the statements above, the variable x will still have the value of 5. The value of x is not reset (or cleared) when you redeclare it.
If you assign values to variables that have not yet been declared, the variables will automatically be declared.
These statements:
| x=5; carname="Volvo"; |
have the same effect as:
| var x=5; var carname="Volvo"; |
Creating variables in JavaScript is most often referred to as "declaring" variables.
You can declare JavaScript variables with the var statement:
| var x; var carname; |
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:
| var x=5; var carname="Volvo"; |
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.
As with algebra, JavaScript variables are used to hold values or expressions.
A variable can have a short name, like x, or a more descriptive name, like carname.
Rules for JavaScript variable names:
Note: Because JavaScript is case-sensitive, variable names are case-sensitive.
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).
