how to prevent duplicated entries in javascript?

Question

i have a problem in preventing duplicates from being entered, i'm generated radio buttons dynamically in 2 pages at the same time using exactly one button, i take the label from the user and generate a radio button from that label, i want to prevent the user from entering 2 identical labels, here's the script which generates radios for the 2 pages any help will be appreciated

function createRadioElement(elem, label, checked) {
var id = 'option1_' + label;
$('#after').append($('<input />', {
    'type': 'radio',
    'fieldset':'group',
    'name': 'option1',
    'id': id,
    'data-role': 'controlgroup',
    'data-theme':'b',
    'value': '1'}));
$('#after').append('<label for="' + id + '">'+ label + '</label>').trigger('create');}

function createRadioFortSecondPage(elem, label, checked) {
var id = 'option1_' + label;
$('#Inserthere').append($('<input />', {
    'type': 'radio',
    'fieldset':'group',
    'name': 'option1',
    'id': id,
    'data-role': 'controlgroup',
    'data-theme':'b',
    'value': '1'}));
$('#Inserthere').append('<label for="' + id + '">'+ label + '</label>').trigger('create');}

that's the function i wrote to prevent duplicates:

function checkDublicates(){
     var isExist=true;
     var x = document.getElementById('option').value;
     var labels = [];   
$('#after input[type=radio]').each(function() {
     labels.push($('label[for='+$(this).attr('id')+']').text());


    });
    for(var i=0;i<labels.length;i++){

    if(x==labels[i])
    {
        isExist=false;}
        else{
        isExist=true;}
      }
    return isExist;}

and that's the button action:

$('#AddButton').click(function(){
     var exist=checkDublicates();
     <!--var isEmpty=validate();-->
    <!--if(exist==true){
        <!--alert("Duplicates Are Not Allowed!");
        <!--}else{
    var y=document.getElementById('question').value
    document.getElementById('headTitle').innerHTML=y;
    if(exist==false){
        alert("Duplicates Not Allowed!")
    }else{
    createRadioElement(this,$('#option').val(),true);
    createRadioFortSecondPage(this,$('#option').val(),true);
  }

  });

Answer 1

Just use $.inArray(val, arr) it will work ! http://api.jquery.com/jQuery.inArray/

But just a comment concerning your code.

Replace

document.getElementById('question').value

by

$('#question').val()

and

document.getElementById('headTitle').innerHTML=y

by

$('#headTitle').html(y)

Will be much cleaner ;-)

Answer 2

You can use this handy function to push elements into an array and check for duplicates at the same time. It'll return true if it catches a duplicate.

var noDupPush = function (value, arr) {

    var isDup = false;

    if (!~$.inArray(value, arr)) {
        arr.push(value);
    } else {
        isDup = true;
    }

    return isDup;

};

// You can use it like this

var arr = ['green'];
if (noDupPush('green', arr)){
  // Dup exists
}
// Or else it will just push new value to array

Answer 3

You could generate an id that includes the text of the label and then very quickly check for the existence of an element containing that text. For example:

function generateLabelId( userinput ){ 
    return 'awesomelabel_' + userinput.replace(/\W/g,'');
}

var label = document.getElementById(generateLabelId( userinput ));
var labelDoesNotExist = (label == undefined );

if (labelDoesNotExist){
    // create your element here
    // making sure that you add the id from generateLabelId
}