/* set up elements on page */
var el1 = document.getElementById("first");
var el2 = document.getElementById("second");
var el3 = document.getElementById("third");
var btn = document.getElementById("insultBtn");

/* populate spans with random insults */
function generateInsult() {
    for( var i = 1; i <= 3; i++ ) {
        var randNbr = Math.round(Math.random()*41);
        eval("el" + i + ".firstChild.nodeValue = col" + i + "[randNbr]");
    }
}

/* attach onclick event to form button */
btn.onclick = generateInsult;