How can I write an angularjs filter to search for string fragments/sequences of strings

Question

I'm trying to write an angularjs custom filter that checks whether an array of countries contains a search string entered by the user.

The string can consist of one letter (e.g. 'E'), or a fragment of n-letters (e.g. 'lan') or an entire word (e.g. 'England').

In every case, all countries containing that one letter or that fragment should be returned, so 'E' would return 'England', 'Estonia' etc. while 'lan' would return 'England', 'Ireland', etc.

So far my filter returns the entire country or single letters but I'm having difficulty with string fragments:

1. HTML Template:

   <input ng-model="filter.text" type="search" placeholder="Filter..."/>
   
   <ul>
      <li ng-repeat="item in data | listfilter:filter.text">
   </ul>
   

2. angularJS

   angular.module('sgComponents').filter('listfilter',[ function () {
   return function(items, searchText) {
       var filtered = [];            
   
       angular.forEach(items, function(item) {
           if(item.label === searchText) { // matches whole word, e.g. 'England'
               filtered.push(item);
           }
           var letters = item.label.split('');
           _.each(letters, function(letter) {
               if (letter === searchText) { // matches single letter, e.g. 'E'
                   console.log('pushing');
                   filtered.push(item);
               }
           });
           // code to match letter fragments, e.g. 'lan'
       });
       return filtered;
   };
   }]);
   

Answer 1

It is much simpler than that, use the String.indexOf() function:

angular.forEach(items, function(item) {
    if( item.label.indexOf(searchText) >= 0 ) filtered.push(item);
});

You may want to turn both strings .toLowerCase() to do case-insensitive matching:

searchText = searchText.toLowerCase();
angular.forEach(items, function(item) {
    if( item.label.toLowerCase().indexOf(searchText) >= 0 ) filtered.push(item);
});