Guide on showcasing an alert notification when the data is already existing within an array through javascript

Need help with displaying an alert message in JavaScript for duplicate values in an array?

var names = [];

var nameInput = document.getElementById("txt1");
var messageBox = document.getElementById("display");

function insert() {
  names.push(nameInput.value);
  clearAndPush();
}

function clearAndPush() {
  nameInput.value = "";
  messageBox.innerHTML = "";
  messageBox.innerHTML += "Names:" + names.join(", ";

  function removeDups(names) {
    let unique = {};
    names.forEach(function (i) {
      if (!unique[i]) {
        unique[i] = true;
      }
    });
    return Object.keys(unique);
  }
  document.getElementById("display").innerHTML = removeDups(names);

<label>Name:</label><input type="text" id="txt1" placeholder="Enter Name">
<input type="button" value="Click" onclick="insert()">

<div id="display"></div>

Answer №1

It seems like your question could use a bit more clarity, but based on my understanding, it appears you are inquiring about how to determine if a value is present in an array. The solution is quite simple - utilize Array.prototype.includes():

if (names.includes(nameInput.value) {
    alert("The name " + nameInput.value + " is already included in the names array.");
}

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