JSFiddle - React, Tailwind, and code Playground

by Rajan Verma

HTML

<select name="n1" id="box_g1">
    <option value="Default">Default</option>
    <option value="A">A</option>
    <option value="B">B</option>
    <option value="C">C</option>
    <option value="D">D</option>
    <option value="E">E</option>
</select>
<br/>

<select name="n2" id="box_g2">
    <option value="Disabled">Disabled</option>
    <option value="A">A</option>
    <option value="B">B</option>
    <option value="C">C</option>
    <option value="D">D</option>
    <option value="E">E</option>
</select>
<br/>
<select name="n3" id="box_g3">
    <option value="Disabled">Disabled</option>
    <option value="A">A</option>
    <option value="B">B</option>
    <option value="C">C</option>
    <option value="D">D</option>
    <option value="E">E</option>
</select>
<br/>
<select name="n4" id="box_g4">
    <option value="Disabled">Disabled</option>
    <option value="A">A</option>
    <option value="B">B</option>
    <option value="C">C</option>
    <option value="D">D</option>
    <option value="E">E</option>
</select>
<br/>
<select name="n5" id="box_g5">
    <option value="Disabled">Disabled</option>
    <option value="A">A</option>
    <option value="B">B</option>
    <option value="C">C</option>
    <option value="D">D</option>
    <option value="E">E</option>
</select>

<br/>
<br/>
<input type="submit" value="Check Result" onclick="checkResult();"/>

JavaScript

var duplicates = [];

function checkResult(){
var box1 = document.getElementById('box_g1');
var box2 = document.getElementById('box_g2');
var box3 = document.getElementById('box_g3');
var box4 = document.getElementById('box_g4');
var box5 = document.getElementById('box_g5');

var b1 = box1.options[box1.selectedIndex].value;
var b2 = box2.options[box2.selectedIndex].value;
var b3 = box3.options[box3.selectedIndex].value;
var b4 = box4.options[box4.selectedIndex].value;
var b5 = box5.options[box5.selectedIndex].value;

var arr  = [b1,b2,b3,b4,b5];
var hash = [];

for (var n=arr.length; n--; ){
   if (typeof hash[arr[n]] === 'undefined' ) hash[arr[n]] = [];
    if(arr[n] != "Disabled"){
        hash[arr[n]].push(n);
    }    
}

for (var key in hash){
    if (hash.hasOwnProperty(key) && hash[key].length > 1){
        duplicates.push(key);
    }
}

if(duplicates.length > 0){
    alert("duplicate found");
}else{
     alert("No duplicate");   
}
duplicates.length =0;    
}