javascript - How to get first characters matching results only in typeahead -

i want show results starting user entered matching characters only. want avoid if occur in middle. how can in typeahead.

here's js code:

var cities = new bloodhound({   datumtokenizer: bloodhound.tokenizers.whitespace,   querytokenizer: bloodhound.tokenizers.whitespace,   prefetch: '/getcities' });  $('#city').typeahead({     hint: true,     highlight: true,     minlength: 3,     limit: 10 }, {   name: 'cities',   source: cities }); 

you have redefine datumtokenizer. example assuming autocompletion values field "key" in array of objects

datumtokenizer: function(d){                         var tokens = [];                         var stringsize = d.key.length;                                                     (var = 0; i<= stringsize; i++){                               tokens.push(d.key.substr(0, i));                           }                         return tokens;                     },