JAVASCRIPT-3 :)

---

JavaScript Functions

• A JavaScript function is a block of code designed to perform a particular task.

• A JavaScript function is executed when “something” invokes it (calls it). ____

JavaScript Function Syntax

function name(parameter1, parameter2, parameter3) {
  // code to be executed
}

Function parameters are listed inside the >parentheses () in the function definition.

Function arguments are the values received by >the function when it is invoked.

Inside the function, the arguments (the parameters) behave as local variables.

Example :

---

Why Functions?

You can reuse code: Define the code once, and use it many times.

You can use the same code many times with different arguments, to produce different results.

note : The () Operator Invokes the Function

---

Functions Used as Variable Values

Functions can be used the same way as you use variables, in all types of formulas, assignments, and calculations.

Example Instead of using a variable to store the return value of a function:

<script>
document.getElementById("demo").innerHTML =
"The temperature is " + toCelsius(77) + " Celsius";

function toCelsius(fahrenheit) {
  return (5/9) * (fahrenheit-32);
} 
</script>

---

Local Variables

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

Local variables can only be accessed from within the function.

// code here can NOT use carName

function myFunction() {
  var carName = "Volvo";
  // code here CAN use carName
}

// code here can NOT use carName

---

Naming Conventions

Always use the same naming convention for all your code. For example:

• Variable and function names written as camelCase

• Global variables written in UPPERCASE (We don’t, but it’s quite common)

• Constants (like PI) written in UPPERCASE