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Splitting code into different files

From: Foundations of Programming: Fundamentals

Video: Splitting code into different files

We can end up with hundreds or thousands of lines of code very quickly. And although we will be splitting them up into functions, they can still get difficult to read and navigate. Another way to make your code more manageable-- and this happens in every programming language-- is we stop trying to keep it all in one file and we just split it up into several files. Now you wouldn't do this randomly. You wouldn't have half a function in one file and half in the other. But you might group several functions together in one file and several more in another. This also makes it easier for multiple people to work on the same project by working on separate files.

Splitting code into different files

We can end up with hundreds or thousands of lines of code very quickly. And although we will be splitting them up into functions, they can still get difficult to read and navigate. Another way to make your code more manageable-- and this happens in every programming language-- is we stop trying to keep it all in one file and we just split it up into several files. Now you wouldn't do this randomly. You wouldn't have half a function in one file and half in the other. But you might group several functions together in one file and several more in another. This also makes it easier for multiple people to work on the same project by working on separate files.

And in complex applications built by teams of software developers, it's not unusual to have hundreds or thousands of separate code files for one project. Now JavaScript isn't a language that you would want to split up into hundreds or thousands of files. It's unusual to have more than a handful. The question is if you do split it up, how does the web page know where to find everything? But we have seen that the way that we tell our HTML page where our JavaScript is, is we use a script tag. This is what we've been using all along and if we split our JavaScript into multiple files we simply add more script tags. That's it.

The JavaScript engine, the interpreter that's built into the browser, will load all of these and run the code inside all of these files. Now because the JavaScript engine will try and run your code as soon as it gets its hands on it, order can be important here. So let's say we are linking to three separate JavaScript files, script.js, morefunctions.js, and functions.js. Let's say we have a bunch of really important functions that are going to be called by some code in our script.js file.

Well, by default what's going to happen is the JavaScript engine is going to try and run the code in script.js as soon as it loads it. If it's looking for functions that it hasn't gone to yet we are going to have a problem. So order is important. Just be aware of any dependencies that you might be creating and whether you've loaded all the code you need to load. To make sure those important functions are loaded into the interpreter first. Now having said that for us, this won't be an issue. In this course, it's perfectly acceptable to keep all the things in one script file.

But for future reference, and particularly with other languages, you will see the code that you work with typically split up into different files to make it easier to work on.

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This video is part of

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Foundations of Programming: Fundamentals

61 video lessons · 92262 viewers

Simon Allardice
Author

 
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  1. 4m 15s
    1. Welcome
      1m 17s
    2. Making the most of this course
      2m 8s
    3. Using the exercise files
      50s
  2. 22m 11s
    1. What is programming?
      5m 45s
    2. What is a programming language?
      4m 48s
    3. Writing source code
      5m 34s
    4. Compiled and interpreted languages
      6m 4s
  3. 16m 29s
    1. Why JavaScript?
      4m 45s
    2. Creating your first program in JavaScript
      6m 54s
    3. Requesting input
      4m 50s
  4. 31m 38s
    1. Introduction to variables and data types
      5m 16s
    2. Understanding strong, weak, and duck-typed languages
      3m 51s
    3. Working with numbers
      5m 4s
    4. Using characters and strings
      4m 5s
    5. Working with operators
      4m 47s
    6. Properly using white space
      6m 46s
    7. Adding comments to code for human understanding
      1m 49s
  5. 24m 48s
    1. Building with the if statement
      7m 35s
    2. Working with complex conditions
      4m 9s
    3. Setting comparison operators
      6m 59s
    4. Using the switch statement
      6m 5s
  6. 17m 54s
    1. Breaking your code apart
      4m 1s
    2. Creating and calling functions
      2m 56s
    3. Setting parameters and arguments
      6m 7s
    4. Understanding variable scope
      2m 23s
    5. Splitting code into different files
      2m 27s
  7. 13m 31s
    1. Introduction to iteration
      4m 28s
    2. Writing a while statement
      5m 24s
    3. Creating a for loop
      3m 39s
  8. 19m 28s
    1. Cleaning up with string concatenation
      4m 30s
    2. Finding patterns in strings
      8m 3s
    3. Introduction to regular expressions
      6m 55s
  9. 19m 58s
    1. Working with arrays
      5m 46s
    2. Array behavior
      5m 29s
    3. Iterating through collections
      5m 18s
    4. Collections in other languages
      3m 25s
  10. 10m 50s
    1. Programming style
      5m 55s
    2. Writing pseudocode
      4m 55s
  11. 25m 55s
    1. Input/output and persistence
      3m 6s
    2. Reading and writing from the DOM
      8m 11s
    3. Event driven programming
      7m 47s
    4. Introduction to file I/O
      6m 51s
  12. 24m 25s
    1. Introduction to debugging
      5m 57s
    2. Tracing through a section of code
      7m 5s
    3. Understanding error messages
      3m 21s
    4. Using debuggers
      8m 2s
  13. 14m 16s
    1. Introduction to object-oriented languages
      5m 18s
    2. Using classes and objects
      6m 28s
    3. Reviewing object-oriented languages
      2m 30s
  14. 11m 14s
    1. Memory management across languages
      5m 11s
    2. Introduction to algorithms
      4m 2s
    3. Introduction to multithreading
      2m 1s
  15. 29m 20s
    1. Introduction to languages
      1m 42s
    2. C-based languages
      4m 40s
    3. The Java world
      3m 13s
    4. .NET languages: C# and Visual Basic .NET
      6m 17s
    5. Ruby
      3m 4s
    6. Python
      2m 56s
    7. Objective-C
      4m 3s
    8. Libraries and frameworks
      3m 25s
  16. 1m 2s
    1. Where to go from here
      1m 2s

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