如何验证jQuery中输入字段是否已更改

Question

The method I wrote checks if the date has inserted/changed in input field, and I want to trig confirm message to the user when this condition is true. The problem that the confirm message is triggered every time even when the date has not changed. My method looks like below:

   var alertuserSave = function() {
        val4 = $("#ContentPlaceHolder1_txtFinalized").val();
         var alrt_value = document.createElement("INPUT");
         alrt_value.type = "hidden";
         alrt_value.name = "confirm_value";
         if ((val3 === "5" || val3 === "6") && val4) {
         confirm("Remember to Save the inserted data.");
         alrt_value.value = "Yes";
         } else {
             alrt_value.value = "No";
         }


         document.forms[0].appendChild(alrt_value);
     }

And I added a listener on document load like this:

var val3 = $('#ContentPlaceHolder1_ddlResponsibility').val();
    var val4 = $("#ContentPlaceHolder1_txtFinalized").val();
    console.log(val4 + " is val4 ")
    $(document).ready(function() {
        $("#ContentPlaceHolder1_txtFinalized").change(alertuserSave);

How to make the pop up fired only when the date has changed and not every time?

Answer 1

val4 = $("#ContentPlaceHolder1_txtFinalized").val();

returns the value of the element

so if you check:

(...  && val4) 

it is always true

you need to check something like:

val4 != oldvalue