Javascript variable always be declared inside script tag.

<script>
var x=15;
var y=16;
var sum=x+y;
document.writeln("Sum ="+sum);
</script>

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Declare variables in Javascript

JavaScript where to declare variables

To declare a variable in JavaScript me must follow the syntax. As given below

Syntax

<script language="javascript">

//  declare variable or do your calculation

  </script>"

See an example given below that show how to declare a variable in JavaScript.

<Script Language="JavaScript">

var name, age;

name = Java;
age = 7;
document.write(name);
document.write("<br>");
document.write(age);
</Script>

In the above example name and age are two variable and further we have assigned some value to it. Always remember that the variable name must be written in small letters. document.write (); is used to print the value of variable.