Simpel antiSpam javascript

simpelAntiSpam.js

function antiSpam(sIDOfFormToWatch, preInfo, postInfo) {
    preInfo = (preInfo || 'This page is being spammed.\nPlease confirm that you are human by entering: "');
    postInfo = (postInfo || '"');
    var s = document.getElementById(sIDOfFormToWatch);
    if (s === null) return;
    var oldSubmit = s.onsubmit;
    if (s === null) oldSubmit = function() {
        return true;
    };
    s.onsubmit = function(t) {
        var r = parseInt(Math.random() * 1000);
        if (prompt(preInfo + r + postInfo, '') != r) {
            return false;
        } else {
            oldForm.call(this, t);
        }
        return false;
    };
}