Getting started with understanding JavaScript variables and getting started with javascript

Getting started with understanding JavaScript variables and getting started with javascript

Variables are containers used to store information:

 

x=5; length=66.10;

Do you still remember the Algebra I learned at school?

When you recall the algebra courses you have learned at school, you may think of x = 5, y = 6, z = x + y, and so on.

 

Remember, a letter can save a value (for example, 5), and the above information can be used to calculate that the value of z is 11.

 

You must have forgotten it, right.

 

These letters are called variables and can be used to save values (x = 5) or expressions (z = x + y ).

JavaScript Variables

Like algebra, JavaScript variables are used to save values or expressions.

 

You can give the variable a brief name, such as x or a descriptive name, such as length.

 

JavaScript variables can also save text values, such as carname = "Volvo ".

 

Rules for JavaScript variable names:

Variables are case sensitive (y and Y are two different variables)

The variable must start with a letter or underscore

Note: JavaScript is case sensitive and variable names are also case sensitive.

Instance

You can change the value of a variable during script execution. You can reference a variable by its name to display or change its value.

This example shows how it works.

Declare (create) JavaScript Variables

Variable creation in JavaScript is often called a "Declaration" variable.

 

You can declare JavaScript variables using the var statement:

 

var x;var carname;

After the preceding Declaration, variables have no values, but you can assign values to them when declaring them:

 

var x=5;var carname="Volvo";

Note: When assigning a text value to a variable, enclose the value with quotation marks.

Assign values to JavaScript Variables

Assign values to JavaScript variables using the assignment statement:

 

x=5;carname="Volvo";

 

The variable name is on the left of the = symbol, and the value to be assigned to the variable is on the right of the = symbol.

 

After the preceding statement is executed, the value saved in variable x is 5, and the carname value is Volvo.
Assign values to undeclared JavaScript Variables

If the variable you assign has not been declared, the variable is automatically declared.

These statements:

 

x=5;carname="Volvo";

The effects of these statements are the same:

 

var x=5;var carname="Volvo";

Redeclare JavaScript Variables

If you declare a JavaScript variable again, the variable will not lose its original value.

 

var x=5;var x;

After the preceding statement is executed, the value of variable x is still 5. When the variable is declared again, the value of x is not reset or cleared.

JavaScript Arithmetic

Like algebra, you can use JavaScript variables for arithmetic:

 

y=x-5;z=y+5;