A function is a group of reusable code which can be called anywhere in your program. This eliminates the need of writing the same code again and again. It helps programmers in writing modular codes. Functions allow a programmer to divide a big program into a number of small and manageable functions. The most common way to define a function in JavaScript is by using the function keyword, followed by a unique function name, a list of parameters (that might be empty), and a statement block surrounded by curly braces. A JavaScript function can have an optional return statement. This is required if you want to return a value from a function. This statement should be the last statement in a function. In the above program, variable x is used to store the function. Here the function is treated as an expression. And the function is called using the variable name. The function above is called an anonymous function.

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Atal Bihari Vajpayee Vishwavidyalaya
Session 2020-21
Subject :-Internet Technologies
Submitted By
Ujjwal Matoliya
Topic :-functions

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Function
Function Definition
Calling a Function
Function Parameters
Function Return
Function Expressions
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3. Function
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A function is a group of reusable code which can be called
anywhere in your program. This eliminates the need of writing
the same code again and again. It helps programmers in writing
modular codes. Functions allow a programmer to divide a big
program into a number of small and manageable functions.
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Function Declaretion
The most common way to
define a function in
JavaScript is by using
the function keyword,
followed by a unique function
name, a list of parameters
(that might be empty), and a
statement block surrounded
by curly braces.
Syntax
<script type = "text/javascript">
<!-- function
functionname(parameter-list)
{ statements }
//-->
</script>
<script type = "text/javascript">
<!-- function sayHello()
{ alert("Hello there"); }
//-->
</script>

5. Calling a Function
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Output
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Function Parameters
A function can also be declared with parameters. A parameter is a value
that is passed when declaring a function.
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program to add two numbers using a function Parameters
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Function Return
A JavaScript function can have an optional return statement. This is required
if you want to return a value from a function. This statement should be the
last statement in a function.
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Function Expressions
In Javascript, functions can also be defined as expressions.
In the above program, variable x is used to store the function. Here the
function is treated as an expression. And the function is called using the
variable name.
The function above is called an anonymous function.
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Benefits of Using a Function
Function makes the code reusable. You can
declare it once and use it multiple times.
Function makes the program easier as each
small task is divided into a function.
Function increases readability.
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