Added nextUid() function for unified way of generating IDs in angular

mhevery · mhevery · commit 02dbf41b3e52 · 2011-05-17T13:23:46.000-07:00
diff --git a/src/Angular.js b/src/Angular.js
@@ -114,6 +114,7 @@ var $$element         = '$element',
     angularCallbacks  = extensionMap(angular, 'callbacks'),
     nodeName_,
     rngScript         = /^(|.*\/)angular(-.*?)?(\.min)?.js(\?[^#]*)?(#(.*))?$/,
+    uid               = ['0', '0', '0'];
     DATE_ISOSTRING_LN = 24;
 
 /**
@@ -188,6 +189,36 @@ function formatError(arg) {
   return arg;
 }
 
+/**
+ * @description
+ * A consistent way of creating unique IDs in angular. The ID is a sequence of alpha numeric
+ * characters such as '012ABC'. The reason why we are not using simply a number counter is that
+ * the number string gets longer over time, and it can also overflow, where as the the nextId
+ * will grow much slower, it is a string, and it will never overflow.
+ *
+ * @returns an unique alpha-numeric string
+ */
+function nextUid() {
+  var index = uid.length;
+  var digit;
+
+  while(index) {
+    index--;
+    digit = uid[index].charCodeAt(0);
+    if (digit == 57 /*'9'*/) {
+      uid[index] = 'A';
+      return uid.join('');
+    }
+    if (digit == 90  /*'Z'*/) {
+      uid[index] = '0';
+    } else {
+      uid[index] = String.fromCharCode(digit + 1);
+      return uid.join('');
+    }
+  }
+  uid.unshift('0');
+  return uid.join('');
+}
 
 /**
  * @workInProgress
diff --git a/test/AngularSpec.js b/test/AngularSpec.js
@@ -583,4 +583,22 @@ describe('angular', function(){
       });
     }
   });
+
+
+  describe('nextUid()', function(){
+    it('should retun new id per call', function(){
+      var last;
+      var current;
+      var count = 100;
+
+      last = nextUid();
+      while(count--) {
+        current = nextUid();
+        expect(current.match(/[\d\w]+/)).toBeTruthy();
+        expect(last).not.toEqual(current);
+        last = current;
+      }
+    });
+  });
+
 });
