Codjo #2 - by @leotrs and @jajoosam

sortedSearch.js

function sortedSearch(listy, x) {
    var start = 0;
    var end = listy.length-1;
    var index = Math.round((end+start)/2);
    var i = 0;
    while (listy[index] != x && i<listy.length/2) {

        if(x<listy[index]){
            end = index;
        }
        else {
            start = index;
        }
        index = Math.round((end+start)/2);
        i++;
    }

    if(i<listy.length/2){
      return index;
    }
    else{
      return -1;
    }

}