WIP - %f conversion specifier

lib/util.js

@@ -22,7 +22,22 @@
 var events = require('events');
 
 
-var formatRegExp = /%[sdj%]/g;
+/**
+ * Format a floating point value.
+ * @param value Floating point value to format.
+ * @param precision Precision in decimals after the dot (1, 2, 3, etc.).
+ */
+var MULTIPLIERS = [1, 10, 100, 1000, 10000];
+function format_float(value, precision) {
+  if (!precision) return ~~value + ''; // integer part only
+  var multiplier = MULTIPLIERS[precision] || Math.pow(10, precision);
+  value = 5 + ~~(value * multiplier * 10);
+  value = (value - (value % 10)) / 10;
+  return ~~(value / multiplier) + '.' + ('' + value).slice(-precision);
+}
+
+
+var formatRegExp = /%[sdj%]|%(\.\d*)?f/g;
 exports.format = function(f) {
   if (typeof f !== 'string') {
     var objects = [];
@@ -34,14 +49,18 @@ exports.format = function(f) {
 
   var i = 1;
   var args = arguments;
-  var str = String(f).replace(formatRegExp, function(x) {
-    switch (x) {
+  var str = String(f).replace(formatRegExp, function(s) {
+    switch (s) {
       case '%s': return String(args[i++]);
       case '%d': return Number(args[i++]);
       case '%j': return JSON.stringify(args[i++]);
       case '%%': return '%';
       default:
-        return x;
+        if (s[s.length-1] === 'f') {
+          var precision = s.slice(2, -1) || 6; // 6 = default precision
+          return format_float(args[i++], ~~precision);
+        }
+        return s;
     }
   });
   for (var len = args.length, x = args[i]; i < len; x = args[++i]) {