From e92f3fb68665da6fd2a0948b81ea5c007b6d5903 Mon Sep 17 00:00:00 2001
From: Mike Bostock <mbostock@gmail.com>
Date: Thu, 7 Jan 2016 13:50:48 -0800
Subject: [PATCH] Fix #17 - implement format.toString.

---
 src/locale.js       | 14 ++++++++++----
 test/format-test.js |  5 +++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/locale.js b/src/locale.js
index b500b10..70eba3e 100644
--- a/src/locale.js
+++ b/src/locale.js
@@ -15,7 +15,7 @@ export default function(locale) {
       currency = locale.currency,
       decimal = locale.decimal;
 
-  function format(specifier) {
+  function newFormat(specifier) {
     specifier = formatSpecifier(specifier);
 
     var fill = specifier.fill,
@@ -47,7 +47,7 @@ export default function(locale) {
         : /[gprs]/.test(type) ? Math.max(1, Math.min(21, precision))
         : Math.max(0, Math.min(20, precision));
 
-    return function(value) {
+    function format(value) {
       var valuePrefix = prefix,
           valueSuffix = suffix;
 
@@ -115,10 +115,16 @@ export default function(locale) {
       }
       return padding + valuePrefix + value + valueSuffix;
     };
+
+    format.toString = function() {
+      return specifier + "";
+    };
+
+    return format;
   }
 
   function formatPrefix(specifier, value) {
-    var f = format((specifier = formatSpecifier(specifier), specifier.type = "f", specifier)),
+    var f = newFormat((specifier = formatSpecifier(specifier), specifier.type = "f", specifier)),
         e = Math.max(-8, Math.min(8, Math.floor(exponent(value) / 3))) * 3,
         k = Math.pow(10, -e),
         prefix = prefixes[8 + e / 3];
@@ -128,7 +134,7 @@ export default function(locale) {
   }
 
   return {
-    format: format,
+    format: newFormat,
     formatPrefix: formatPrefix
   };
 };
diff --git a/test/format-test.js b/test/format-test.js
index a1e962d..c667eb9 100644
--- a/test/format-test.js
+++ b/test/format-test.js
@@ -6,6 +6,11 @@ tape("format(specifier)(number) returns a string", function(test) {
   test.end();
 });
 
+tape("format(specifier).toString() returns the normalized specifier", function(test) {
+  test.equal(format.format("d") + "", " >-d");
+  test.end();
+});
+
 tape("format(specifier) throws an error for invalid formats", function(test) {
   test.throws(function() { format.format("foo"); }, /invalid format: foo/);
   test.throws(function() { format.format(".-2s"); }, /invalid format: \.-2s/);