fix multiply with precision, fixes #76

scurker · Dec 28, 2017 · 8b5850f · 8b5850f
1 parent 62517ed
commit 8b5850f
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Showing 2 changed files with 20 additions and 4 deletions.
diff --git a/src/currency.js b/src/currency.js
@@ -7,6 +7,8 @@ const defaults = {
   precision: 2
 };
 
+const pow = p => Math.pow(10, p);
+
 const regex = {
   groupedNumbers: /(\d)(?=(\d{3})+\b)/g,
   lastDecimal: /\.(\d+)$/
@@ -25,7 +27,7 @@ function currency(value, opts) {
   }
 
   let settings = Object.assign({}, defaults, opts)
-    , precision = Math.pow(10, settings.precision)
+    , precision = pow(settings.precision)
     , v = parse(value, settings);
 
   that.intValue = v;
@@ -39,7 +41,7 @@ function currency(value, opts) {
 function parse(value, opts, round = true) {
   let v = 0
     , { decimal, errorOnInvalid, precision: decimals } = opts
-    , precision = Math.pow(10, decimals);
+    , precision = pow(decimals);
 
   if (typeof value === 'number') {
     v = value * precision;
@@ -95,7 +97,7 @@ currency.prototype = {
    */
   multiply(number) {
     let { intValue, _settings } = this;
-    return currency((intValue *= parse(number, _settings, false)) / Math.pow(10, _settings.precision + 2), _settings);
+    return currency((intValue *= number) / pow(_settings.precision), _settings);
   },
 
   /**

diff --git a/test/test.js b/test/test.js
@@ -81,14 +81,28 @@ test('should subtract floating point', t => {
 
 test('currency multiplication', t => {
   var value = currency(1.23).multiply(2);
-  t.is(parseFloat(value), 2.46, 'currency(1.23).multiplication(2) is 2.46');
+  var floatingValue = currency(.1).multiply(.2);
+
+  t.is(parseFloat(value), 2.46, 'currency(1.23).multiply(2) is 2.46');
+  t.is(parseFloat(floatingValue), .02, 'currency(.1).multiply(.2) equals 0.02');
+  t.not(parseFloat(floatingValue), .1*.2, 'currency(.1).multiply(.2) does not equal 0.020000000000000004');
+});
+
+test('currency multiplication with precision', t => {
+  var value = currency(1.369, { precision: 3 }).multiply(3);
+  t.is(parseFloat(value), 4.107, 'currency(1.369).multiply(3) is 4.107');
 });
 
 test('currency division', t => {
   var value = currency(9.87).divide(2);
   t.is(parseFloat(value), 4.93, 'currency(9.87).divide(2) is 4.93');
 });
 
+test('currency division with precision', t => {
+  var value = currency(4.107, { precision: 3 }).divide(3);
+  t.is(parseFloat(value), 1.369, 'currency(4.107).divide(3) is 1.369');
+});
+
 test('should parse negative values', t => {
   var pos = currency(1.23),
       neg = currency(-1.23),