How to make an addition instead of a concatenation

Question

I have an input button. I created for this input an attribute called \"multiplicateur\" which has the value of 1. When the button is clicked I have a .click() t

Answer 1

ajaxData is a string. Thus, you need to parse it to an integer...

 $('#envoyer').click(function() {
    const ajaxData = $(this).attr('multiplicateur');

    /* parse string to integer */
    alert(parseInt(ajaxData) + 1);

});