#JavaScript Functions

##Objectives

	- Understand what a JavaScript function is
	- Be able to recognize a function syntax
	- Understand how to write a constructor function

###What is a JavaScript function?

`In JavaScript, a function can be both a method AND a class.`

###Using JS functions as a subroutine

	A JavaScript function is essentially a block of code to do a particular task. Sometimes you will hear them being referred to as methods or subroutines. In the Object-Oriented Programming (OOP) paradigm, think of it like behaviors.

- To use JavaScript as a method, you will have to 1) define the method and 2) invoke it.

**`Demo`**

	// Define our function with a parameter name

	function sayHi(name){
		// write a message saying hi
		console.log('Hi, I am ' + name);
	}

	// Invoke our function with the argument 'Stanley'

	sayHi('Stanley');

####Activity
***

	Write a function that does a square root of any integer argument and test it on the numbers 4, 6, and 22

#####Part II

	Write a check in the function that ensures only a number can be inserted. Return false if the parameter is not an integer

**Solution:**

	function squareRoot(num){
	  if(typeof num==='number' && (num%1)===0){
    	return num * num;
	  }else{
   		return false;
  	  }
	}

	console.log(square(4));
	console.log(square(6));
	console.log(square(8));
	console.log(square('hello world'));

#####Part III

	Partner up with the person next to you and create a JS function that convert Fahrenheit to Celsius

	function toCelsius(fahrenheit){
		return (fahrenheit - 32)/(1.8);
	}

	console.log(toCelsius(100));

###What the heck is a class?

	A class is a simply template to create objects!

For instance, let's create a human class

	// Define the class
	function Human(name){

		this.name = name;
		this.sayHi = function(){
			console.log('Hi, my name is ' + this.name);
	}

	// Initialize the object utilizing the 'new' keyword
	var Stanley = new Human('Stanley');
	Stanley.sayHi();

###What the heck is `this`

The `this` keyword in javascript, in a constructor function context, refers to the the Object once its been initialized with the `new` keyword.

However, keep in mind, in a global context, `this` refers to the window object

####Activity
***

Now, make your person be able to calculate the square root of numbers

Then

Make your person be able to convert fahrenheit to celsius!

###Questions

- What are the two main purposes of using functions in JavaScript?
- What is this keyword refer to in the global context?
- What is the syntax for writing a basic subroutine?