In this example, x, y, and z, are variables:
From the example above, you can expect:
In this example, price1, price2, and total, are variables:
In programming, just like in algebra, we use variables (like price1) to hold values.
In programming, just like in algebra, we use variables in expressions (total = price1 + price2).
From the example above, you can calculate the total to be 11.
These unique names are called identifiers.
Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).
The general rules for constructing names for variables (unique identifiers) are:
=) is an "assignment" operator, not an "equal to" operator.
This is different from algebra. The following does not make sense in algebra:
(It calculates the value of x + 5 and puts the result into x. The value of x is incremented by 5.)
The "equal to" operator is written like
In programming, text values are called text strings.
Strings are written inside double or single quotes. Numbers are written without quotes.
If you put a number in quotes, it will be treated as a text string.
After the declaration, the variable has no value (technically it has the value of
To assign a value to the variable, use the equal sign:
You can also assign a value to the variable when you declare it:
In the example below, we create a variable called carName and assign the value "Volvo" to it.
Then we "output" the value inside an HTML paragraph with id="demo":
It's a good programming practice to declare all variables at the beginning of a script.
You can declare many variables in one statement.
Start the statement with
var and separate the variables by comma:
A declaration can span multiple lines:
In computer programs, variables are often declared without a value. The value can be something that has to be calculated, or something that will be provided later, like user input.
A variable declared without a value will have the value
The variable carName will have the value
undefined after the execution of this statement:
The variable carName will still have the value "Volvo" after the execution of these statements:
You can also add strings, but strings will be concatenated:
Also try this:
If you put a number in quotes, the rest of the numbers will be treated as strings, and concatenated.
Now try this: