jQuery Uncaught TypeError: $.strength is not a function

[bojates]

Is there an example of this working somewhere? I can't get the jQuery element to work. I get the error: Uncaught TypeError: $.strength is not a function

I've installed via the gem into a Rails 4.2 app. Application.js has:

//= require jquery
//= require bootstrap-sprockets
//= require jquery_ujs
//= require jquery.turbolinks
//= require turbolinks
//= require password_strength
//= require jquery_strength
//= require_tree .

I have not also put the JavaScript in my assets dir. I've confirmed (using Chrome Developer tools) that the scripts are being included in the page. I have tried to include them in a different order after the jquery, but it hasn't helped.

In my application.js I have

$.strength("#user_email", "#user_password");

and get the error in the console.

A working version to look at would be useful, or any pointers if I'm doing something obviously wrong.

Thank you!