Merge pull request chuanxshi#156 from georgezafiris/master

chuanxshi · web-flow · commit 19ddc1ea5523 · 2018-06-10T23:09:10.000+08:00
For-in loop with object properties' existence check
diff --git a/general-patterns/for-in-loops.html b/general-patterns/for-in-loops.html
@@ -1,4 +1,4 @@
- <!doctype html>
+<!doctype html>
 <html lang="en">
 	<head>
 		<title>JavaScript Patterns</title>
@@ -9,22 +9,19 @@
 			/* Title: for-in loops
 			 * Description: optimized for-in loops
 			 */
-
 			// the object
 			var man ={
 				hands:2,
 				legs:2,
 				heads:1
 			};
-
 			// somewhere else in the code
 			// a method was added to all objects
 			if (typeof Object.prototype.clone === 'undefined'){
 				Object.prototype.clone = function (){
 				};
 			}
-
-
+			
 			// antipattern
 			// for-in loop without checking hasOwnProperty()
 			for (var i in man){
@@ -37,32 +34,25 @@
 			 * heads : 1
 			 * clone: function()
 			 */
-
-
 			// preferred 1
 			for (var i in man){
 				if (man.hasOwnProperty(i)){// filter
 					console.log(i, ":", man[i]);
 				}
 			}
-
 			/*
 			 * result in the console
 			 * hands : 2
 			 * legs : 2
 			 * heads : 1
 			 */
-
-
 			// preferred 2
 			// benefit is you can avoid naming collisions in case the `man` object has redefined `hasOwnProperty`
 			for (var i in man){
 				if (Object.prototype.hasOwnProperty.call(man, i)){// filter
 					console.log(i, ":", man[i]);
 				}
 			}
-
-
 			// preferred 3
 			// use a local variable to "cache" `Object.prototype.hasOwnProperty`
 			var i,
@@ -72,8 +62,28 @@
 					console.log(i, ":", man[i]);
 				}
 			}
-
-
+			
+			
+			//Preferred 4 
+			/* Check if object has properties before print output
+			 * using Object.keys(obj) and length built ins. A good method for 
+			 * not wasting resources and avoiding errors with larger objects
+			 */ 
+			if (Object.keys(man).length > 0){
+			 for (var item in man)
+				 console.log(item,':',man[item]);
+			} else{
+			 console.log('Empty Object')}
+			
+			/*	
+			 * hands : 2
+			 * legs : 2
+			 * heads : 1
+			 * clone : function(){
+			 *		 }
+			 */
+			
+			
 			// References
 			// http://net.tutsplus.com/tutorials/javascript-ajax/the-essentials-of-writing-high-quality-javascript/
 		</script>
