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Using semicolons makes it possible to write multiple statements on one line.

JavaScript code (or just JavaScript) is a sequence of JavaScript statements.

JavaScript statements can be grouped together in blocks. Blocks start with a left curly bracket {, and ends with a right curly bracket }.

The purpose of a block is to make the sequence of statements execute together.

Normally a block is used to group statements together in a function or in a condition (where a group of statements should be executed if a condition is met).

<script type="text/javascript"> function show_alert() { alert("I am an alert box!"); } </script>

Confirm Box A confirm box is often used if you want the user to verify or accept something. When a confirm box pops up, the user will have to click either "OK" or "Cancel" to proceed. If the user clicks "OK", the box returns true. If the user clicks "Cancel", the box returns false. Syntax confirm("sometext");

<script type="text/javascript"> function show_confirm() { var r=confirm("Press a button"); if (r==true)   {   alert("You pressed OK!");   } else   {   alert("You pressed Cancel!");   } } </script>

Prompt Box A prompt box is often used if you want the user to input a value before entering a page. When a prompt box pops up, the user will have to click either "OK" or "Cancel" to proceed after entering an input value. If the user clicks "OK" the box returns the input value. If the user clicks "Cancel" the box returns null. Syntax prompt("sometext","defaultvalue");

<script type="text/javascript"> function show_prompt() { var name=prompt("Please enter your name","Harry Potter"); if (name!=null && name!="")   {   document.write("Hello " + name + "! How are you today?");   } } </script>

to provide computer access to non-science students. At the time, nearly all use of computers required writing custom software, which was something only scientists and mathematicians tended to do.