JSFiddle - React, Tailwind, and code Playground

by James

HTML

<input type="text" id="YourElement" value="bla, ble, string1" />

JavaScript

//Create an array from the CSV list
var myVals = $("#YourElement").val().split(",");
var isDupe = false;

for(var i = 0; i < myVals.length; i++) {
    if(myVals[i].indexOf("YourNewValue") != -1) {
        isDupe = true;
        break;
    }
}

//use .push() to append your value to the end of the array
if(!isDupe) {
    myVals.push("YourNewValue");

    //Invoking .toString() on an array creates a CSV list
    $("#YourElement").val(myVals.toString());
}