Filter method is throwing error while running on android device


I am having issue with ionic v1 project. i am using this method to search
$ = $ => {
return ($scope.srch.toLowerCase()) > -1);

this is working fine in browser but when i am trying to run the android build its throwing error during the loading of the app.

" Uncaught SyntaxError: Unexpected token { "

Please help me with this issue. thanks.