andreloster

var array = [{a:"word",b:"world"},{a:"2015",b:"people"}];
var result = -1;
for(var i=0; i<array.length; i++) {
    for(var key in array[i]) {
        if(array[i][key] == "people")    result = i;
    }
    if(result > -1)    break;
}

document.write(result);

<script type="text/javascript" src="http://code.jquery.com/jquery-1.11.1.min.js"></script>

.slider-controls {
position:absolute;
left:50%;  /* калибруйте */
bottom:12px;
text-align:center;
}