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vidhya murali
vidhya murali

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Functions in JavaScript

#webdev #ai #programming #javascript

JavaScript Functions

Functions are Code Blocks

  • Functions are reusable code blocks designed to perform a particular task.
  • Functions are executed when they are called or invoked.
  • Functions are fundamental in all programming languages.

They allow you to organize, reuse, and modularize code. It can take inputs, perform actions, and return outputs.

Why Use Functions?

Functions help you to:

  • Reuse code (write once, run many times)
  • Organize code into smaller parts
  • Make code easier to read and maintain

What Does a Function Look Like?

A function can be created with the function keyword, a name, and parentheses.

The code to run is written inside curly brackets

The function above does not do anything.It has to be called first.

Functions Run When You Call Them

To run a function, you call it by using its name followed by parentheses like sayHello().

Note:() means execute now.

JavaScript Function Syntax

function name( p1, p2, ... ) {
// code to be executed
}

Functions are defined with the function keyword:

  • followed by the function name
  • followed by parentheses ( )
  • followed by brackets { }
  • The function name follows the naming rules for variables.

Optional parameters are listed inside parentheses: ( p1, p2, ... )

Code to be executed is listed inside curly brackets: { }

Functions can return an optional value back to the caller.

  • A function definition is not an executable statement.
  • It is not common to end a function definition with a semicolon.
  • Semicolons are used to separate executable JavaScript statements.

A Function Can Be Used Many Times

A big benefit is that you can call the same function whenever you need it.

Example :

    function add(a, b) {
     return a + b;
    }

    let sum1 = add(5, 5);
    let sum2 = add(50, 50);
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Note : values returned from functions can be stored in variables

Local Variables

Variables declared within a JavaScript function, become LOCAL to the function.

Local variables can only be accessed from within the function.

Example :

 // code here can NOT use carName
      function myFunction() {
         let carName = "Volvo";
    // code here CAN use carName
   }

// code here can NOT use carName
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Since local variables are only recognized inside their functions, variables with the same name can be used in different functions

Local variables are created when a function starts, and deleted when the function is completed.

Function Input and Output

The most useful functions work like this:

  • Parameters - some values are sent to the function
  • Arguments - some values are received by the function
  • Function Code - some work is done inside the function
  • Return Output - some value is returned from the function

Reference :https://www.w3schools.com/js/js_function_intro.asp

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