Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Example: Resize

From: JavaScript Essential Training

Video: Example: Resize

So let's deconstruct another example. More than ever, these days we need to realize that the amount of screen real estate we have varies widely, from 30-inch-wide monitors to iPads, iPhones, and other smartphones. Now here's one JavaScript approach for dealing with this. Let's say I have a screen design for a typical desktop, and it looks pretty good, but if I resize and make it smaller, to something like a smartphone, what it does is change itself pretty significantly with the layout. Again, wider, we see a very visual display; narrow, we see a text-focused display.

Example: Resize

So let's deconstruct another example. More than ever, these days we need to realize that the amount of screen real estate we have varies widely, from 30-inch-wide monitors to iPads, iPhones, and other smartphones. Now here's one JavaScript approach for dealing with this. Let's say I have a screen design for a typical desktop, and it looks pretty good, but if I resize and make it smaller, to something like a smartphone, what it does is change itself pretty significantly with the layout. Again, wider, we see a very visual display; narrow, we see a text-focused display.

And the steps to do this are actually very, very simple. One, we need to write JavaScript that realizes when the screen is being resized, and two, we need to then detect the actual size of the screen, because we need to figure out is it getting made smaller or is it getting made wider and change the DOM in reaction to that. Now I could start changing individual attributes of DOM elements if I wanted to and affect things with a fine scalpel, but that's not really what I'm going to do.

Instead in this case, all I'm doing is changing out the entire CSS file that this page is using from main.css, which is the default highly visual file, to narrow.css. And if I take a quick look at those, main.css is my big CSS file with a lot of stuff and narrow.css, well, there is really not much to this. In fact, this one is even doing some basic tricks like hiding all the images. So it's pretty sparse, but it proves the point. My question is well, how do you change them? And I change the CSS file by reaching into my link tag.

Now up to this point, we've really been working with more visual elements, things like paragraphs and list items. But there is no reason why I can't just find, say, a link element. In this case, it has an id of myCSS, and I swap out the CSS file by just affecting the attributes of my link element. Now, this might be stored in the head section of my document, but it's perfectly accessible using JavaScript. We have been used, so far, to affecting things like paragraphs and list items, but there is nothing to stop us grabbing hold of this.

We give it an ID, in this case my CSS, and I can change the attributes of this just as easily as changing attributes of any other element. So if I jump over to the script.js file, I can see what we are doing here. There's an event on the window object called onresize. We have been working with onload so far, which gets called once when the DOM fully loads, but onresize gets called multiple times when you start to resize the browser window; in fact, it gets called dozens of times. It all depends on how fast your machine actually is.

It might get called a lot. So do be aware of that if the function that you are calling actually does a lot of processing. So every time it detects that the window is being resized, it will call the function called adjustStyle. That's the whole breakdown here. So the question is, what is adjustStyle? Well, it looks like there's a lot of code going on here, but in fact, we're back mainly to cross-browser issues. All I really want to do is get the width in pixels, and I create a new variable called width here. But unfortunately, there's not a super-reliable property that I can just access, because it's different across browsers.

So what's happening here is we're doing another little object detection here and saying hey, do I have a window.innerHeight object? If I do, well, then I must have a window.innerWidth object. If I don't, then there is all sorts of other combinations of do I have a documentElement object, and a clientHeight object? If so, I can access clientWidth. You should not bother about memorizing this, because you're typically not going to use it. You are going either copy it from somewhere else or use a third-party library. The end result is we should have a variable called width. And in my case here, what I'm saying is if width as measured as being less than 600, I am going to take grab the CSS element and then set the attribute called href = css/narrow.css, the path to the narrow file.

If it's not less than 600, we will set it to the default one. That's pretty much it. Saving that, if we open up this page, that's what detects, as we do the resize, resize down, it will change to the narrow.css. We resize up, it will change to the wide one. Now the only last thing worth pointing out is this. Let's say I resize down to a fairly small size here and then I reload the page, which as far as JavaScript is concerned means we are loading from scratch. Well, there is the problem; we are loading the default.css file here.

That's because we are not actually resizing, so this is never being called. We are just opening the browser at a small size. So one of the things I really want to do here is just duplicate this function to make sure that when we do an onload the function is also called. This will only happen one extra time, so that shouldn't be a problem. Now when I refresh this page, we should load in at the correct size. Again, this is a simple example that takes us through multiple real-world requirements.

We are dealing with events. We are dealing with affecting the DOM, even if we are grabbing and changing a non-visible element like link. And we are working with feature detection and object detection to deal with cross-browser issues, very much day-to-day tasks for someone working with JavaScript. And a third-party library like jQuery would let me write simpler code here and not actually worry about all this code to deal with cross-browser issues. And in a production site that's typically what I'll use, because I have more than one place that's going to need it.

Show transcript

This video is part of

Image for JavaScript Essential Training
JavaScript Essential Training

56 video lessons · 102223 viewers

Simon Allardice
Author

 
Expand all | Collapse all
  1. 3m 28s
    1. Welcome
      1m 1s
    2. What you should know
      1m 44s
    3. Using the exercise files
      43s
  2. 15m 41s
    1. Introduction to JavaScript
      8m 6s
    2. Creating your first JavaScript
      2m 13s
    3. Getting to know the tools and applications
      5m 22s
  3. 56m 8s
    1. Understanding the structure of JavaScript code
      7m 9s
    2. Where to write your JavaScript
      3m 56s
    3. Creating variables
      6m 21s
    4. Working with conditional code
      5m 44s
    5. Working with operators
      13m 28s
    6. Sending messages to the console
      2m 59s
    7. Working with loops
      8m 1s
    8. Creating functions
      8m 30s
  4. 36m 13s
    1. Working with arrays
      7m 57s
    2. Working with numbers
      6m 13s
    3. Working with strings
      8m 27s
    4. Working with dates
      5m 38s
    5. Working with objects
      7m 58s
  5. 9m 6s
    1. What is the DOM?
      5m 49s
    2. Working with nodes and elements
      3m 17s
  6. 25m 17s
    1. Accessing DOM elements
      11m 3s
    2. Changing DOM elements
      5m 42s
    3. Creating DOM elements
      8m 32s
  7. 24m 45s
    1. Introduction to JavaScript event handling
      8m 16s
    2. Working with onClick and onLoad events
      7m 36s
    3. Working with onBlur and onFocus events
      2m 36s
    4. Working with timers
      6m 17s
  8. 21m 41s
    1. Common JavaScript errors
      7m 14s
    2. Using Firebug
      4m 7s
    3. Going through a debugging session
      10m 20s
  9. 10m 13s
    1. Accessing form elements
      4m 20s
    2. Preventing a form from being submitted
      2m 36s
    3. Hiding and showing form sections
      3m 17s
  10. 9m 49s
    1. CSS and JavaScript
      3m 46s
    2. Removing and applying CSS classes
      2m 16s
    3. Changing inline styles
      3m 47s
  11. 19m 44s
    1. Understanding JavaScript style
      7m 39s
    2. Minifying your code
      4m 28s
    3. Using JavaScript code checkers
      7m 37s
  12. 22m 24s
    1. Introduction to JavaScript libraries
      3m 17s
    2. Linking to multiple JavaScript files
      2m 11s
    3. Introduction to jQuery
      12m 7s
    4. Using a content distribution network to deliver JavaScript files
      4m 49s
  13. 17m 35s
    1. JavaScript in HTML5
      9m 37s
    2. Using Modernizr
      3m 2s
    3. Using Strict Mode
      4m 56s
  14. 33m 3s
    1. Knowing the JavaScript to avoid
      6m 35s
    2. Introduction to regular expressions
      6m 56s
    3. Working with AJAX
      10m 44s
    4. Working with objects and prototypes
      8m 48s
  15. 21m 10s
    1. Example: Countdown
      8m 3s
    2. Example: Resize
      5m 47s
    3. Example: Accordion
      7m 20s
  16. 4m 58s
    1. Where to go from here
      4m 0s
    2. Goodbye
      58s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ.

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Join now "Already a member? Log in

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed JavaScript Essential Training.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferencesfrom the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Are you sure you want to delete this note?

No

Your file was successfully uploaded.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.