1st dup using map

by Matthew Vasallo

HTML

<ul id="theList">
    <li>6</li>
    <li>3</li>
    <li>1</li>
    <li>4</li>
    <li>7</li>
    <li>4</li>
    <li>2</li>
    <li>8</li>
    <li>9</li>
    <li>2</li>
</ul>

JavaScript

/*
Write an algorithm that will find the first duplicate in a list on the page.
For example we would return 4, for the list above.
*/

var ints = document.querySelectorAll("")

var findDuplicates = function(a) { 
    var matches = []; 
    var match = -1;   
    a.map(function(e, i, c) {
        if (matches[e]) { 
           break;      
        } else { 
           match[e] = true;      
        }    
    })
    return match; 
}