JSFiddle - React, Tailwind, and code Playground

HTML

<select class="requiredAttr">
<option value="">Please select</option>
<option value="1">1</option>
<option value="2">2</option>
</select>
<button>
Validate
</button>

JavaScript

function validate()
{
    $(".requiredAttr").each(function(){
    if($.trim($(this).val()) == ""){
        alert("Please fill in all the required fields.");
        $(this).focus();
        return false;

    }else{
        return true;
    }
    });
    return false;
}

$("button").click(validate);