function greetingHandler() {
    // Declare the variables we will need
    var nameField, resultPar;
    var name, greeting;

    // Gather the page elements we need to interact with
    nameField = document.getElementById('name');
    resultPar = document.getElementById('result');

    // Get the name the user entered.
    name = nameField.value;

    // Construct a greeting
    greeting = 'Hello, ' + name + '. Welcome to JavaScript!';

    // Present the result
    resultPar.textContent = greeting;
}

function setup() {
    var greetingButton;

    greetingButton = document.getElementById('greeting');
    greetingButton.addEventListener('click',greetingHandler,false);
}

window.addEventListener('load',setup,false);