Allow to use function as liveSearchStyle (#2332)

* Allow to use function as liveSearchStyle

Fix #2042

Author: cedk

docs/docs/options.md

@@ -133,10 +133,10 @@ Options can be passed via data attributes or JavaScript. For data attributes, ap
   </tr>
   <tr>
     <td>liveSearchStyle</td>
-    <td>string</td>
+    <td>string | function</td>
     <td><code>'contains'</code></td>
     <td>
-      <p>When set to <code>'contains'</code>, searching will reveal options that contain the searched text. For example, searching for pl with return both Ap<b>pl</b>e, <b>Pl</b>um, and <b>Pl</b>antain. When set to <code>'startsWith'</code>, searching for pl will return only <b>Pl</b>um and <b>Pl</b>antain.</p>
+      <p>When set to <code>'contains'</code>, searching will reveal options that contain the searched text. For example, searching for pl with return both Ap<b>pl</b>e, <b>Pl</b>um, and <b>Pl</b>antain. When set to <code>'startsWith'</code>, searching for pl will return only <b>Pl</b>um and <b>Pl</b>antain. If a function is used, the arguments are the option string and the searched text and it must return <code>true</code> if the option matches or <code>false<code>.</p>
     </td>
   </tr>
   <tr>
@@ -488,4 +488,4 @@ $('#yourSelect').selectpicker({
 });
 ```
 
-For performance reasons, our built-in sanitizer accepts an array of DOM nodes as its first argument, rather than an HTML string. Keep that in mind if deciding to use your own `sanitizeFn`.
+For performance reasons, our built-in sanitizer accepts an array of DOM nodes as its first argument, rather than an HTML string. Keep that in mind if deciding to use your own `sanitizeFn`.

js/bootstrap-select.js

@@ -394,7 +394,9 @@
         if (normalize) string = normalizeToBase(string);
         string = string.toUpperCase();
 
-        if (method === 'contains') {
+        if (typeof method === 'function') {
+            searchSuccess = method(string, searchString);
+        } else if (method === 'contains') {
           searchSuccess = string.indexOf(searchString) >= 0;
         } else {
           searchSuccess = string.startsWith(searchString);