add limitSigDigs() function to number's prototype. tests included

git-svn-id: http://svn.openlayers.org/trunk/openlayers@1008 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Util.js

@@ -707,6 +707,22 @@ Array.prototype.indexOf = function(element) {
     return index;    
 }
 
+/**
+ * @param {int} sig
+ * 
+ * @returns The number, rounded to the specified number of significant digits.
+ *          If null, 0, or negaive value passed in, returns 0
+ * @type int
+ */
+Number.prototype.limitSigDigs = function(sig) {
+    var number = (sig > 0) ? this.toString() : 0;
+    if (sig < number.length) {
+        var exp = number.length - sig;
+        number = Math.round( this / Math.pow(10, exp)) * Math.pow(10, exp);
+    }
+    return parseInt(number);
+}
+
 /**
  * @param {String} id
  * @param {OpenLayers.Pixel} px

tests/test_Util.html

@@ -393,7 +393,7 @@
         t.eq(uObj[bKey.toUpperCase()], bValue, "new uppercase value present");
     }
     
-    function test_10_Util_createUniqueID(t) {
+    function test_11_Util_createUniqueID(t) {
         t.plan(2);
         
         var id = OpenLayers.Util.createUniqueID();
@@ -402,6 +402,33 @@
         var id = OpenLayers.Util.createUniqueID("chicken");
         t.ok( id.startsWith("chicken"), "OpenLayers.Util.createUniqueID starts id correctly");
     }
+    
+    function test_12_Util_limitSigDigs(t) {
+
+        t.plan(7);
+
+        var x;
+
+        x = 123456;
+        t.eq(x.limitSigDigs(3), 123000, "correctly rounds down");
+
+        x = 555555;
+        t.eq(x.limitSigDigs(3), 556000, "correctly rounds up");
+
+        x = 66;
+        t.eq(x.limitSigDigs(3), 66, "correctly handles number smaller than sigdig");
+
+        t.eq(x.limitSigDigs(null), 0, "correctly handles null sigdig");
+        t.eq(x.limitSigDigs(0), 0, "correctly handles 0 sigdig");
+        t.eq(x.limitSigDigs(-1), 0, "correctly handles negative sigdig");
+
+        x = 0;
+        t.eq(x.limitSigDigs(2), 0, "correctly handles 0 number");
+
+
+
+    }
+
   // -->
   </script>
 </head>