support scientific notation in number values

Fixes #37

Author: chearon

lib/unit.js

@@ -1,41 +1,47 @@
 var minus = '-'.charCodeAt(0);
 var plus  = '+'.charCodeAt(0);
 var dot   = '.'.charCodeAt(0);
+var exp   = 'e'.charCodeAt(0);
+var EXP   = 'E'.charCodeAt(0);
 
 module.exports = function (value) {
     var pos = 0;
     var length = value.length;
     var dotted = false;
+    var sciPos = -1;
     var containsNumber = false;
     var code;
-    var number = '';
 
     while (pos < length) {
         code = value.charCodeAt(pos);
 
         if (code >= 48 && code <= 57) {
-            number += value[pos];
             containsNumber = true;
+        } else if (code === exp || code === EXP) {
+            if (sciPos > -1) {
+                break;
+            }
+            sciPos = pos;
         } else if (code === dot) {
             if (dotted) {
                 break;
             }
             dotted = true;
-            number += value[pos];
         } else if (code === plus || code === minus) {
             if (pos !== 0) {
                 break;
             }
-            number += value[pos];
         } else {
             break;
         }
 
         pos += 1;
     }
 
+    if (sciPos + 1 === pos) pos--;
+
     return containsNumber ? {
-        number: number,
+        number: value.slice(0, pos),
         unit: value.slice(pos)
     } : false;
 };

test/unit.js

@@ -25,6 +25,21 @@ var tests = [{
 }, {
     fixture: '.rem',
     expected: false
+}, {
+    fixture: '1e4px',
+    expected: { number: '1e4', unit: 'px' }
+}, {
+    fixture: '1em',
+    expected: { number: '1', unit: 'em' }
+}, {
+    fixture: '1e10',
+    expected: { number: '1e10', unit: '' }
+}, {
+    fixture: '',
+    expected: false
+}, {
+    fixture: 'e',
+    expected: false
 }];
 
 test('Unit', function (t) {