How to pass a variable from HTML to node.js

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HTML

Node.js

So I have this app that reads a file uploaded from the client (index.html) I want to get the file that was uploaded on html and user it on my app.js to read it.
How do I do that.
Here goes the files bellow:

index.html

 <input type="file" id="myFile" name="filename">
 <input type="submit">

app.js

 var fs = require('fs');
 var readMe = fs.readFileSync(??? , 'utf8');
 console.log(readMe);

What I have tried:

I have tried this way:

var file = ("document.getElementById("")");