javascript-patterns/general-patterns/globals.html at master · Pythoning/javascript-patterns · GitHub

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<!doctype html>
<html lang="en">
	<head>
		<title>JavaScript Patterns</title>
		<meta charset="utf-8">
	</head>
	<body>
		<script>
			/* Title: The Problem with Globals
			 * Description: The problem is that they are shared among all the code in your JavaScript application or web page
			 */

			// antipatten 1
			function sum(x, y) {
				// implied global
				result = x + y;
				return result;
			}


			// preferred 1
			function sum(x, y) {
				// a variable declared inside of a function is local to that function and not available outside the function
				var result = x + y;
				return result;
			}


			// antipattern 2
			function foo() {
				var a = b = 0;
				// ...
			}

			// the preceding code snippet will behave as if you've typed the following
			var a = (b = 0);


			// preferred 2
			function foo() {
				var a, b;
				// ...
				a = b = 0; // both local
			}

			// References
			// http://net.tutsplus.com/tutorials/javascript-ajax/the-essentials-of-writing-high-quality-javascript/
		</script>
	</body>
</html>