javascript - Backbone search collection for model that has attribute that matches string -

i writing search function @ moment backbone application, idea user can enter string , app search , return matching models string appears in of attributes. far have following,

view function run on keyup,

this.results = this.collection.search(letters); 

this runs following code located in collection,

search: function( filtervalue ) {      filtervalue = filtervalue.tolowercase();      var filterthroughvalue = function(data) {          return _.some(_.values(data.tojson()), function(value) {             console.log(value);             if(value != undefined) {                 value = (!isnan(value) ? value.tostring() : value);                 return value.tolowercase().indexof(filtervalue) >= 0;             }         });     };      return app.collections.filtercollection = this.filter(filterthroughvalue); } 

however running following error,

uncaught typeerror: undefined not function

this error shown being line return value.tolowercase().indexof(filtervalue) >= 0; , error gets returned whether or not use string know exists in model of collection.

is there fix this, or better way of searching , returning models have models contain search string?

since want string representation of value, can check if value has tostring method. note string has tostring method, work if value string.

return _.some(_.values(data.tojson()), function(value) {   if(value && value.tostring) {     return value.tostring().tolowercase().indexof(filtervalue) >= 0;   }   return false; }