Using Variables in Javascript

Variables are used to store values (name = "John") or expressions (sum = x + y). Before using a variable, you first need to declare it. You have to use the keyword var to declare a variable like this:
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var name;
You can assign a value to the variable either while declaring the variable or after declaring the variable.
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var name = "John";
OR
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var name;
name = "John";
Naming Variables
Though you can name the variables as you like, it is a good programming practice to give descriptive and meaningful names to the variables. Moreover, variable names should start with a letter and they are case sensitive. Hence the variables studentname and studentName are different because the letter n in name is different (n and N).
Try this yourself:
This code is editable. Click Run to Execute
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    <html>
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    <head>
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    <title>Variables!!!</title>
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    <script type="text/javascript">
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    var one = 22;
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    var two = 3;
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    var add = one + two;
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    var minus = one - two;
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    var multiply = one * two;
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    var divide = one/two;
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    document.write("First No: = " + one + "<br />Second No: = " + two + " <br />");
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    document.write(one + " + " + two + " = " + add + "<br/>");
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    document.write(one + " - " + two + " = " + minus + "<br/>");
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    document.write(one + " * " + two + " = " + multiply + "<br/>");
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    document.write(one + " / " + two + " = " + divide + "<br/>");
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    </script>
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    </head>
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    <body>
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    </body>
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    </html>
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