Added character start to fn call arguments per issue #8

index.js

@@ -28,6 +28,9 @@ var flatten = require('lodash.flatten');
  * @return {array}
  */
 function replaceString(str, match, fn) {
+  var curCharStart = 0;
+  var curCharLen = 0;
+
   if (str === '') {
     return str;
   } else if (!str || !isString(str)) {
@@ -44,7 +47,10 @@ function replaceString(str, match, fn) {
 
   // Apply fn to all odd elements
   for (var i = 1, length = result.length; i < length; i += 2) {
-    result[i] = fn(result[i], i);
+    curCharLen = result[i].length;
+    curCharStart += result[i - 1].length;
+    result[i] = fn(result[i], i, curCharStart);
+    curCharStart += curCharLen;
   }
 
   return result;

readme.md

@@ -135,10 +135,10 @@ reactStringReplace('hey hey you', /(hey)/g, () => <span>hey</span>);
 
 Type: `function`
 
-The replacer function to run each time `match` is found. This function will be patched the matching string and an index which can be used for adding keys to replacement components if necessary.
+The replacer function to run each time `match` is found. This function will be patched the matching string and an `index` which can be used for adding keys to replacement components if necessary. Character `offset` identifies the position of match start in the provided text.
 
 ```js
-const func = (match, index) => <span key={index}>{match}</span>;
+const func = (match, index, offset) => <span key={index}>{match}</span>;
 reactStringReplace('hey hey you', /(hey)/g, func);
 ```
 

test.js

@@ -11,6 +11,14 @@ test('Returns an array', t => {
   t.true(Array.isArray(replaceString('blah', 'blah', x => x)));
 });
 
+test('Returns correct character offsets', t => {
+  const correctOffsets = [6, 17];
+  const charOffsets = [];
+
+  replaceString('Hey there, stranger', 'er', (m, i, o) => charOffsets.push(o));
+  t.deepEqual(charOffsets, correctOffsets);
+});
+
 test('Works with matching groups', t => {
   t.deepEqual(
     replaceString('hey there', /(hey)/g, x => ({ worked: x })),