Super simple script to enforce required fields in form. Just add a "required" attribute to the tag. If its blank, it adds some bootstrap error classes to the parent form-group container. Also validates e-mail fields.

required-fields-validation.js

var invalid_fields = 0; //global var can be accessed without calling function
function validate()
{
    invalid_fields = 0; // reset counter
    
    $("[required]").each(function(){
       var val = $(this).val();
       
       if(val == "" || val == null || val.match('/select/i'))
       {
            $(this).closest('.form-group').addClass('has-error has-danger');
            invalid_fields++;
       }
       else
       {
            $(this).closest('.form-group').removeClass('has-error has-danger');
       }

    });

    $("[type='email']").each(function(){
       if( !/[a-z]+@[a-z]+\.[a-z]+/.test( $(this).val() ))
       {
            $(this).closest('.form-group').addClass('has-error has-danger');
            invalid_fields++;
       }
       else
       {
            $(this).closest('.form-group').removeClass('has-error has-danger');   
       }
    });
    return invalid_fields;
}