How to set ByDefault item value in ejs-dropdownlist ?

Then check with the index property

dropObject.index = 0;

Set  dropObject.value = 0; Not working

var focusNullDesignation = false;

 function addNullDesignation() {
     if (!focusNullDesignation) {
         var dropObject = document.getElementById("drpDesignationGroup")["ej2_instances"][0];

         // Add "ALL" item at the first position
         dropObject.addItem({ Value: 0, Text: "ALL" }, 0);

         // Add "Null Designations" item at the second position
         dropObject.addItem({ Value: -1, Text: "Null Designations" }, 1);

         // Set "ALL" as the default selected item using the value property
         dropObject.value = 0;

         // Update the dropdown list
         dropObject.dataBind();
     }
     focusNullDesignation = true;
 }

screenshot my output

Actual Need to

you just need to assign the value of the option you want as selected, as in your case you want "ALL" so do this

 dropObject.value = 0;

To set the default selected item to “ALL”, you can add a line of code to select the “ALL” item after adding it. Here’s how you can modify your addNullDesignation function:

function addNullDesignation() {
    if (!focusNullDesignation) {
        var dropObject = document.getElementById("drpDesignationGroup")["ej2_instances"][0];

        // Add "ALL" item at the first position
        dropObject.addItem({ Value: 0, Text: "ALL" }, 0);

        // Add "Null Designations" item at the second position
        dropObject.addItem({ Value: -1, Text: "Null Designations" }, 1);

        // Set the selected item to "ALL"
        dropObject.value = 0;

        // Update the dropdown list
        dropObject.dataBind();
    }
    focusNullDesignation = true;
}

This will set the default selected item to “ALL” when the dropdown list is focused. The dropObject.value = 0; line sets the selected item to the one with a value of 0, which is “ALL”.