Practice Set, Week 9, Event Handling and Bubbling

for CSCI E3, Harvard University author(s): Larry Bouthillier

by mspears

HTML

<h3>Practice Set, Week 9, Event Handling and Bubbling</h3>

<p>This page contains two buttons, each with an event handler that causes the button, when clicked to echo its text to the page.</p>
<p>Your task is to rewrite the event handling code so that there is only one event handling function. That function should be called when a user clicks on <i>either</i> button. The output should remain identical. </p>
<p>You'll want to consider attaching a single event handler to a node further up the DOM tree, and checking there for which element was actually clicked (using a conditional). </p>
<p>Hint: this is exactly the process that's demonstrated in the video in Week 9 Lesson 2</p>
<div id="container">
    <h4 id="output"></h4>
    <button id="happyBtn">Coding can be fun!</button>
    <button id="gloomyBtn">Coding can be maddening!</button>
</div>

CSS

.button {
    text-indent:0;
    border:1px solid #eda933;
    display:inline-block;
    color:#ffffff;
    font-family:Arial;
    font-size:15px;
    font-weight:bold;
    font-style:normal;
    height:65px;
    line-height:65px;
    padding: .5 em;
    text-decoration:none;
    text-align:center;
    text-shadow:1px 1px 0px #cd8a15;
    background-color:#f6b33d;
}

JavaScript

var container = document.getElementById("container");
container.addEventListener("click", logMessageAlt);
// Utility function for logging convenience
// Logs msg to the element with given id
// If id is undefined, logs to #output
function logMessageAlt(event){
    if (event.target.nodeName === "BUTTON") {
    	document.getElementById("output").innerHTML += event.target.innerHTML +  "<br>";
    }
}