Handle rounding issues

Author: MoOx

index.js

@@ -8,6 +8,7 @@ var reduceFunctionCall = require("reduce-function-call")
  * Constantes
  */
 var MAX_STACK = 100 // should be enough for a single calc()...
+var DECIMAL_PRECISION = 10000 // 5 decimals
 
 /**
  * Global variables
@@ -97,6 +98,10 @@ function evaluateExpression (expression, functionIdentifier, call) {
   // Transform back to a percentage result:
   if (unit === "%") {
     result *= 100
+
+    // adjust rounding shit
+    // (0.1 * 0.2 === 0.020000000000000004)
+    result = Math.round(result * DECIMAL_PRECISION) / DECIMAL_PRECISION
   }
 
   // We don't need units for zero values...

test/index.js

@@ -72,6 +72,11 @@ test("reduce prefixed css calc()", function(t) {
   t.end()
 })
 
+test("handle rounding issues", function(t) {
+  t.equal(reduceCSSCalc("calc(10% * 20%)"), "2%", "should round percentage")
+  t.end()
+})
+
 test("ignore unrecognized values", function(t) {
   t.equal(reduceCSSCalc("calc((4px * 2) + 4.2 + a1 + (2rem * .4))"), "calc(8px + 4.2 + a1 + 0.8rem)", "ignore when eval fail")
   t.end()