Javascript Scope

gistfile1.js

function calculateHeight(startPoint, endPoint) {
  // This function has access to startPoint and endPoint. Nothing else does. 
	return Math.abs(startPoint - endPoint)
}

function calculateWidth(startWidth, endWidth) {
	// Function arguments act as local. ie. startWidth here is local
	// This function has access to startWidth and endWidth. Nothing else does. 
	// Does this have access to a, b, x, y? No
	// Does this have access to q? No
	// Does this have access to z? YES. It is global
	// Does this have access to marker? YES. It is global. 
	alert(z);
	return Math.abs(startWidth - endWidth);
}

function calculateArea(x, y, a, b){
  // This function has access to x, y, a, b
  var q = 100; 		// This is local to just this function
  z = 200;     		// this is global. Don't do this!
  alert(marker);	// This has access to marker
  return calculateHeight(x, y) + calculateWidth(a, b);
}

// If there's a Javascript library that uses "marker" it can access this as well.
// Anything declared outside of a function is global to everything. 
var marker = "green"; // This is accessible in calculateArea. Its GLOBAL
// Same thing as doing marker = "green";

calculateArea(100, 200, 300, 400);