Various JavaScript Statements

JavaScript is Case Sensitive

Unlike HTML, JavaScript is case sensitive – therefore watch your capitalization closely when you write JavaScript statements, create or call variables, objects and functions.

JavaScript Statements

A JavaScript statement is a command to a browser. The purpose of the command is to tell the browser what to do.

This JavaScript statement tells the browser to write “Hello Dolly” to the web page:
document.write(“Hello Dolly”);

It is normal to add a semicolon at the end of each executable statement. Most people think this is a good programming practice, and most often you will see this in JavaScript examples on the web.
The semicolon is optional (according to the JavaScript standard), and the browser is supposed to interpret the end of the line as the end of the statement. Because of this you will often see examples without the semicolon at the end.

JavaScript Code

JavaScript code (or just JavaScript) is a sequence of JavaScript statements.
Each statement is executed by the browser in the sequence they are written.
This example will write a heading and two paragraphs to a web page:

Example

<script type=”text/javascript”>
document.write(“<h1>This is a heading</h1>”);
document.write(“<p>This is a paragraph.</p>”);
document.write(“<p>This is another paragraph.</p>”);
</script>

JavaScript Blocks

JavaScript statements can be grouped together in blocks.
Blocks start with a left curly bracket {, and end with a right curly bracket }.
The purpose of a block is to make the sequence of statements execute together.
This example will write a heading and two paragraphs to a web page:

Example

<script type=”text/javascript”>{
document.write(“<h1>This is a heading</h1>”);
document.write(“<p>This is a paragraph.</p>”);
document.write(“<p>This is another paragraph.</p>”);}
</script>

It just demonstrates the use of a block. 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).

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Different between JavaScript into <head></head> and into <body></body>

JavaScript between <head></head> Tag :

JavaScript between<head></head> tag generally writing as a function & function call from HTML content of the webpage, like this :

Here I have made a JavaScript function “displaydate()” between <head></head> tag and calling this function inside html content. According to function it will display date into “<p id=”demo”></p>”



<html>
<head>
<script type=”text/javascript”>

function displaydate(){

document.getElementById(“demo”).innerHTML=Date();

}

</script>
</head>
<body>

<h1>My First Web Page</h1>

<p id=”demo”></p>
<script type=”text/javascript”>displaydate();</script>
</body>

</html>


Now JavaScript between<body></body> Tag :

JavaScript between <body></body> tag generally writing as a function or inline code, like this :

Here I just wrote a inline JavaScript code to display date” between <body></body> tag. There not need to call any function, when page request date will show on page. According to function it will display code into “<p id=”demo”></p>”
<html>

<head></head>

<body>

<h1>My First Web Page</h1>
<p id=”demo”></p>
<script type=”text/javascript”>document.getElementById(“demo”).innerHTML=Date();</script>
</body>

</html>

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