Can not do document.getElementID from other js beside app.js

[nhuymat1]

Thanks for sharing the code. I just taking some steps in node opencv. The problem is when I want to have a slider in index.html and get the value of the slider to socket.js to control how blur the background can be. The 'document is not define' keeps pop up in socket.js but I can get the slider value in app.js. Please help!!