JSFiddle - React, Tailwind, and code Playground

HTML

<div id="profile-list">
    
</div>

JavaScript

var classes = ['email-checkout', 'absc', 'random', 'brrrr'];

for(var i = 0; i < 2000; i++){
    $('<input />').attr({
        type: 'checkbox', 
        class: classes[Math.floor(Math.random() * classes.length)], 
        checked: (Math.random() > .5)
    }).appendTo('#profile-list');
}

var checkboxLength = 'Checkbox length: ' + $('.email-checkout').length;

// Original (minus the table bit)

var start = (new Date()).getTime(), 
    elements = $("#profile-list input[type=checkbox].email-checkout:not(:checked)");

$.each(elements, function(i) {
    $(elements[i]).attr('checked', 'checked');
});

var now = (new Date).getTime(), 
    originalRunTime = 'Original: ' + (now - start); 

// Reset

$("#profile-list :checkbox.email-checkout").each(function(){
    this.checked = (Math.random() > .5);
});

// New

start = (new Date).getTime();

$("#profile-list :checkbox.email-checkout").each(function(){
    this.checked = true;
});

var now = (new Date).getTime(), 
    newRunTime = 'New: ' + (now - start);

$('body').empty().append(checkboxLength + ' ' + originalRunTime + ' ' + newRunTime);