<html>
<body>
<script>
document.write("Hello World!")
</script>
</body>
</html>
Output: Hello World!
End of Statement =>> Semicolon Used
If a single statement is finished it will be defined by a semi colons in most of the Programming Languages. But JS allows your code If you won't add a semi colon. Anyway writing with Semi colon is best idea. (It is a good programming practice to use semicolons.)
JavaScript is a Case Sensitive language as most of the Programming Languages.
This means that the language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.
So, name , Name are different according to JavaScript...
Comments in JavaScript
For single line comment we use : //
For multi line comment we use : /* line goes here /*
JavaScript Identifiers
All JavaScript variables must be identified with unique names.
These unique names are called identifiers.
Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).
The general rules for constructing names for variables are:
- Names can contain letters, digits, underscores, and dollar signs.
- Names must begin with a letter
- Names can also begin with $ and _
- Names are case sensitive (y and Y are different variables)
- Reserved words (JavaScript keywords) cannot be used as names
Variable
When declaring a variable in JavaScript...
var Syntax is used
Now, In ECMA 6 we can use const & let keyword also..
const means constants and let will change its value if you change the value...
Variable Scope in JS
Global Variable : Global Variable can be defined anywhere in your JavaScript code.
Local Variable : Local Variables can be visible only within a function where it is defined. Function parameters are always local to that function.
Have a look at this code
<html>
<body>
<script >
var myVar = "global"; // Declare a global variable
function parathan( ) {
var myVar = "local"; // Declare a local variable
document.write(myVar);
}
</script>
</body>
</html>
Output : local
as document.write() is printed inside a function & that function contains a myVar variable... So, the output will display "local" only.
If you code document.write() outside the function then the output is "global"
The lifetime of a JavaScript variable starts when it is declared.
Local variables are deleted when the function is completed.
In a web browser, global variables are deleted when you close the browser window (or tab), but remains available to new pages loaded into the same window.
The lifetime of a JavaScript variable starts when it is declared.
Local variables are deleted when the function is completed.
In a web browser, global variables are deleted when you close the browser window (or tab), but remains available to new pages loaded into the same window.
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