added documentation to conditionals

chuanxshi · chuanxshi · commit f3677248f22b · 2012-01-29T23:32:45.000+08:00
diff --git a/general-patterns/conditionals.html b/general-patterns/conditionals.html
@@ -11,20 +11,106 @@
 */
 
 // NOTE: Paul Irish states that the first statement is only an antipattern when optimizing for 
-// low-bandwidth source (such as for a bookmarklet.
+// low-bandwidth source (such as for a bookmarklet).
 // Using the first statement will generally outperform the regex in a loop, and is faster than the
 // object literal for lower numbers of conditions (they generally even out around 10 conditions).
 // See http://jsperf.com/if-this-or-that
 
-// antipattern
+// Normal Pattern
 if (type === 'foo' || type === 'bar' ) {}
 
-// preferred method 1 - regex test
+
+/* alternative method 1 - regex test */
 if ( /^(foo|bar)$/.test(type) ) {}
 
-// preferred method 2 - object literal lookup (smaller if < 5 items)
+
+/* alternative method 2 - object literal lookup (smaller if < 5 items) */
 if ( ({foo:1,bar:1})[type] ) {}
 
+
+/* alternative method 3 - binary-search-like approach
+   This approach is best when there are ranges of values for which to test
+*/
+
+if (value == 0){
+  return result0;
+} else if (value == 1){
+  return result1;
+} else if (value == 2){
+  return result2;
+} else if (value == 3){
+  return result3;
+} else if (value == 4){
+  return result4;
+} else if (value == 5){
+  return result5;
+} else if (value == 6){
+  return result6;
+} else if (value == 7){
+  return result7;
+} else if (value == 8){
+  return result8;
+} else if (value == 9){
+  return result9;
+} else {
+  return result10;
+}
+
+if (value < 6){
+  if (value < 3){
+    if (value == 0){
+      return result0;
+    } else if (value == 1){
+      return result1;
+    } else {
+      return result2;
+    }
+  } else {
+    if (value == 3){
+      return result3;
+    } else if (value == 4){
+      return result4;
+    } else {
+      return result5;
+    }
+  }
+} else {
+  if (value < 8){
+    if (value == 6){
+      return result6;
+    } else {
+      return result7;
+    }
+  } else {
+    if (value == 8){
+      return result8;
+    } else if (value == 9){
+      return result9;
+    } else {
+      return result10;
+    }
+  }
+}
+
+
+/* alternative method 4 - object/array lookup tables
+   Most useful when there is logical mapping between a single key and a single value
+*/
+ 
+if (value == 0) {
+  return result0;
+} else if (value == 1) {
+  return result1;
+} else if (value == 2) {
+  return result2;
+}
+
+// define the array of results
+var results = [result0, result1, result2];
+// return the correct result
+return results[value];
+
+
 // reference
 // http://paulirish.com/2009/perf/
 </script>
