JSFiddle - React, Tailwind, and code Playground

HTML

<!doctype html>
<input autofocus>
<input>

JavaScript

var results = "$('input[autofocus]').length // returns ";
results += $('input[autofocus]').length;
results += "\n\n";
results += "$('input').filter(function(){\n";
results += "    return $(this).attr(\"autofocus\") != null\n";
results += "}).length // returns ";
results += $('input').filter(function(){
    var attr = $(this).attr("autofocus");
    return attr != null && attr !== false;
}).length;

$("body").append("<pre>" + results + "</pre>");