Start learning with our library of video tutorials taught by experts. Get started

JavaScript Essential Training
Illustration by

Linking to multiple JavaScript files


From:

JavaScript Essential Training

with Simon Allardice

Video: Linking to multiple JavaScript files

So I have suggested that your default way of including JavaScript on your page is to have a script tag right before the closing body tag that just links to a separate JavaScript file. And it is also quite common to see several script tags here, and particularly common when it comes to having both your own code and one or more JavaScript libraries and perhaps a link to a Google Analytics JavaScript and so on. But two things to keep in mind: you want to keep the amount of script tags here at a minimum, and the order of them matters. So, why minimum? Well, just be aware that every JavaScript file you link to is a separate request the browser needs to make to the web server.
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

Watch this entire course now—plus get access to every course in the library. Each course includes high-quality videos taught by expert instructors.

Become a member
please wait ...
JavaScript Essential Training
5h 31m Beginner Jul 22, 2011

Viewers: in countries Watching now:

Use JavaScript to add new features and a richer, more compelling user interface on web pages. This course keeps current best practices and practical uses for JavaScript in mind, while covering syntax, working with the DOM, and developing and debugging across multiple platforms, devices, and browsers. Author Simon Allardice also shows how to progressively enhance and gracefully degrade web pages, and take advantage of the world of JavaScript libraries now available.

Topics include:
  • Understanding the structure of JavaScript code
  • Creating variables, functions, and loops
  • Writing conditional code
  • Sending messages to the console
  • Working with different variable types and objects
  • Creating and changing DOM objects
  • Event handling
  • Working with timers
  • Debugging JavaScript
  • Building smarter forms
  • Working with CSS, HTML5, and JavaScript
  • Using regular expressions
Subjects:
Developer Web Web Design Programming Languages Web Development
Software:
JavaScript
Author:
Simon Allardice

Linking to multiple JavaScript files

So I have suggested that your default way of including JavaScript on your page is to have a script tag right before the closing body tag that just links to a separate JavaScript file. And it is also quite common to see several script tags here, and particularly common when it comes to having both your own code and one or more JavaScript libraries and perhaps a link to a Google Analytics JavaScript and so on. But two things to keep in mind: you want to keep the amount of script tags here at a minimum, and the order of them matters. So, why minimum? Well, just be aware that every JavaScript file you link to is a separate request the browser needs to make to the web server.

The browser gets the HTML and moves down through it. It sees the link to the JavaScript and makes a call to the server for that first JavaScript file. It then waits for that file to finish downloading, and then, and only then, moves on to the next one, calls the web server for that file, and waits again. And that order continues. It doesn't download the JavaScript simultaneously. It will do it sequentially. And that means the more files you have the more requests the browser needs to make and the slower your page is going to load.

So while you might find it easy when writing JavaScript to have multiple small files, it's definitely worse for the user. So combine your JavaScript where you can. You should have as few JavaScript files as possible. And secondly, the order of the script tags matters. If you have a file of JavaScript that inside it calls a function in a second JavaScript file, well, you want to make sure to load that file before the code that tries to call this. This is very common with libraries.

If you're using, for example, the jQuery library, you want to make sure that you load jQuery first before any JavaScript that might actually try to use jQuery, and the same goes for any other dependency. So sure, you can't always get this down to just one file, but you should certainly be very careful if you see this growing to seven or a dozen, and see if you can't combine some of them together.

There are currently no FAQs about JavaScript Essential Training.

 
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.
Upgrade now


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 Upgrade now

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

Notes cannot be added for locked videos.

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.