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JavaScript - Variables

Variables

Variables are containers that you can store values in. You start by declaring a variable with the var keyword, followed by any name you want to call it:

var myVariable;

Note: A semicolon at the end of a line indicates where a statement ends; it is only absolutely required when you need to separate statements on a single line. However, some people believe that it is a good practice to put them in at the end of each statement. There are other rules for when you should and shouldn't use

After declaring a variable, you can give it a value:

myVariable = 'Bob';

You can do both these operations on the same line if you wish:

var myVariable = 'Bob';

You can retrieve the value by just calling the variable by name:

myVariable;

After giving a variable a value, you can later choose to change it:

var myVariable = 'Bob';
myVariable = 'Steve';

Note that variables may hold values that have different data types:

Variable	Explanation	Example
String	A sequence of text known as a string. To signify that the value is a string, you must enclose it in quote marks.	`var myVariable = 'Bob';`
Number	A number. Numbers don't have quotes around them.	`var myVariable = 10;`
Boolean	A True/False value. The words `true` and `false` are special keywords in JS, and don't need quotes.	`var myVariable = true;`
Array	A structure that allows you to store multiple values in one single reference.	`var myVariable = [1,'Bob','Steve',10];` Refer to each member of the array like this: `myVariable[0]`, `myVariable[1]`, etc.
Object	Basically, anything. Everything in JavaScript is an object, and can be stored in a variable. Keep this in mind as you learn.	`var myVariable = document.querySelector('h1');` All of the above examples too.

So why do we need variables? Well, variables are needed to do anything interesting in programming. If values couldn't change, then you couldn't do anything dynamic, like personalize a greeting message or change the image displayed in an image gallery.

<html>
   <body>
      <script type="text/javascript ">
      var age = 25;
      var name ="Superman";
           alert( "The age of "+name+"is "+age+" years"); 
    
      </script>  
      <a href="Lesson1a.html ">Back to Lesson</a>
   </body>
</html>

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