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JavaScript Interactive Web Pages with JavaScript Traversing and Manipulating the DOM with JavaScript Traversing Elements

Richard Brinkley
Richard Brinkley
4,807 Points
Posted by Richard Brinkley
Richard Brinkley
4,807 Points

Why use querySelector() to get the "a" element? Wouldn't getElementsByTagName() be a better choice?

In Challenge Task 2 of 2 for Traversing Elements, the question reads:

"On line 14 of the app.js, we want to get the anchor (the a element) from inside the listItem. Use a method to traverse and select the anchor."

The code on line 14 reads: var anchor = listItem;

Given that the anchor tag is an element, and the task was to "get" the anchor element, I used getElementsByTagName(), but the Challenge Task failed. However, I tested this method in the console and it works.

Why?

app.js 
//Select the naviagation
var navigation = document.getElementById("navigation");

//Select all listItems from the navigation
var listItems = navigation.children;

//When a navigation link is pressed
var linkListener = function() {
  console.log("Listener is clicked!");
}

var bindEventsToLinks = function(listItem) {
  //Select the anchor
  var anchor = listItem.querySelector("a");
  //Bind the linkListener to the anchor element (a) 
  anchor.onclick = linkListener;
}



for(var i = 0; i < listItems.length ; i++) {
    bindEventsToLinks(listItems[i]);
}
index.html 
<!DOCTYPE html>
<html>
<head></head>
<body>

<ul id="navigation">
  <li>
    <a href="#home">Home</a>
  </li>
  <li>
    <a href="#about">About</a>
  </li>
  <li>    
    <a href="#contact">Contact</a>
  </li>
</ul>

<p>A few of my favourite things:</p>
<ul>
  <li>
    Rain drops on roses
  </li>
  <li>
    Whiskers on kittens
  </li>
  <li>
    Brown paper packages wrapped up with string
  </li>
</ul>

<script src="app.js"></script>
</body>
</html>

2 Answers

Sean Ahern
Sean Ahern
7,533 Points
Sean Ahern
Sean Ahern
7,533 Points

Hi Richard,

The code that follows this DOM lookup assumes that you will be working with a single element. getElementsByTagName() returns a collection of elements (HTMLCollection) instead of a single element. Note the plurality of "Elements" in the function name. querySelector() will return the first element that matches the given query, which means the .onclick assignment that happens next will work just fine without having to specify an array index.

Karina Machado
Karina Machado
5,999 Points
Karina Machado
Karina Machado
5,999 Points

Sean good example , I get it better now.