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Foundations of Programming: Fundamentals
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Properly using white space


From:

Foundations of Programming: Fundamentals

with Simon Allardice

Video: Properly using white space

JavaScript, like virtually all modern programming languages, does not care about whitespace, and by whitespace I mean spaces, tabs, line breaks. These are all regarded as insignificant, they are ignored. So if I have a file of JavaScript here with multiple statements in it, it doesn't matter if I start putting line breaks in between the lines whether at the start or the end or in the middle. This has no impact on behavior whatsoever. In the same way I've been starting every statement on the first character, but if I decided to put in a few tabs or a few spaces that doesn't matter at all.
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  1. 4m 14s
    1. Welcome
      1m 16s
    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 49s
    1. Building with the if statement
      7m 35s
    2. Working with complex conditions
      4m 10s
    3. Setting comparison operators
      6m 59s
    4. Using the switch statement
      6m 5s
  6. 17m 56s
    1. Breaking your code apart
      4m 1s
    2. Creating and calling functions
      2m 57s
    3. Setting parameters and arguments
      6m 7s
    4. Understanding variable scope
      2m 23s
    5. Splitting code into different files
      2m 28s
  7. 13m 32s
    1. Introduction to iteration
      4m 28s
    2. Writing a while statement
      5m 24s
    3. Creating a for loop
      3m 40s
  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 59s
    1. Working with arrays
      5m 47s
    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 26s
    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 3s
  13. 14m 17s
    1. Introduction to object-oriented languages
      5m 18s
    2. Using classes and objects
      6m 29s
    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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Foundations of Programming: Fundamentals
4h 47m Beginner Sep 22, 2011

Viewers: in countries Watching now:

This course provides the core knowledge to begin programming in any language. Simon Allardice uses JavaScript to explore the core syntax of a programming language, and shows how to write and execute your first application and understand what's going on under the hood. The course covers creating small programs to explore conditions, loops, variables, and expressions; working with different kinds of data and seeing how they affect memory; writing modular code; and how to debug, all using different approaches to constructing software applications.

Finally, the course compares how code is written in several different languages, the libraries and frameworks that have grown around them, and the reasons to choose each one.

Topics include:
  • Writing source code
  • Understanding compiled and interpreted languages
  • Requesting input
  • Working with numbers, characters, strings, and operators
  • Writing conditional code
  • Making the code modular
  • Writing loops
  • Finding patterns in strings
  • Working with arrays and collections
  • Adopting a programming style
  • Reading and writing to various locations
  • Debugging
  • Managing memory usage
  • Learning about other languages
Subjects:
Developer Web Programming Foundations
Author:
Simon Allardice

Properly using white space

JavaScript, like virtually all modern programming languages, does not care about whitespace, and by whitespace I mean spaces, tabs, line breaks. These are all regarded as insignificant, they are ignored. So if I have a file of JavaScript here with multiple statements in it, it doesn't matter if I start putting line breaks in between the lines whether at the start or the end or in the middle. This has no impact on behavior whatsoever. In the same way I've been starting every statement on the first character, but if I decided to put in a few tabs or a few spaces that doesn't matter at all.

The language just doesn't care. It's ignoring the white space and just reading the characters that do occur. It's ignoring the line breaks because we use the semicolon to tell JavaScript where the statement ends. In fact, because we do it this way, if I wanted to, I could actually combine multiple statements onto one line. There is no problem with doing this in JavaScript. It does make our code tougher to read, so I am not going to do this. The general rule is one statement one line, but we could do it that way.

Even inside the statements themselves whitespace is ignored. I could put multiple spaces between the different elements of that statement or on the other hand I could actually get rid of a couple of those spaces. The rule here is don't confuse JavaScript and don't confuse ourselves. While I could have this line, var b=10, squeeze down about this much, I couldn't take it one step further and get rid of this space, because now I am confusing JavaScript. What is varb mean? It needs to be able to figure out where one part ends and the next begins.

So I'll need a space between the var and our variable name b. It's one of the reasons we can't have spaces in our variable names themselves. What I don't need is a space between the variable name here, b, and the equal sign. And that's because JavaScript knows the equal sign is not allowed as part of the variable name so this part must be separate, but best practice there are spaces between the different elements, the different parts of your statement. The only thing that's typical is you don't use a space before the closing semicolon.

Now you could have one. This is perfectly a valid JavaScript, with one space or a dozen before the semicolon. But the way most people write JavaScript and other C-based languages is just to immediately close with the semicolon as soon as you can. It's just the way we finished the line like using the period at the end of a sentence in English. White space more than anything is simply for readability. You start jamming all the elements up against each other, it becomes tough to read. So you use as many spaces as you need to make this clear.

Now there are a few customs that you may run into. Let's say we are using the ++ operator and I am just doing a++ here. I could write this as a ++, but by convention, a simple line like this is just written this way, but that takes us into one more point. There are two places that white space does matter. First, if we are using an operator that has multiple characters like the ++ operator, this is one thing. While I could put a space between the variable name and the ++ and I could put a space between the ++ and the closing semicolon, I cannot put a space in between the two. And that's because as far as JavaScript is concerned, this is not two addition operators.

It is one ++ operator, the increment operator, the ability to add one to a variable. So you can't put a space in the middle of that, same with a --, same with operators like += or -=. You can't put a space in the middle of this just the same way you can't put the space in the middle of var or alert or prompt or a variable name. Now the second place whitespace matters is inside a string. There's a difference between what, space, is, space, your, space, name, and adding a few more spaces to it and that's because we want spaces to matter inside a string.

So when you are creating string literals they will be regarded as significant. Now one question might be what if you want a line break inside a string? Well, for example here I might want to break the line between what is and your name. Now it's an easy thing to think, well, I'll just split that onto another line because after all we're ending the entire statement with the semicolon, so does this work? Well, no, it doesn't. You are not allowed to do it this way. JavaScript will get very confused about what's going on. If you want a line break inside a string, you may have to give JavaScript a clue that this is what we're doing, quite similar to adding the quotes inside a string by using the backslash.

What we use is another backslash to say this is what's called an escape character, there is a special character coming up that means something other than regular text, and then I say \n. Now this looks little weird. It looks like what is \nyour name? But as far as JavaScript is concerned, these two characters here are special. \n means new line, and I am using this string literal in a prompt. So if I save this, let's test this one. I'm going to open up the HTML page that's pointing to this file and as we can see here, the message is now coming out as, What is, line break, your name.

I type in Simon, I click OK, and we get the rather ugly looking message HelloSimon. Well, that's simply because I'm concatenating or combining two strings together here. I've created a variable called message that says Hello and then I'm adding the word Hello and whatever name was typed in and popping that up as an alert box. But really what I want is Hello, space, and then the name. So this would be another reason we would want this space regarded as significant.

So that when we are combining strings together, they don't all jam up against each other. Saving that and trying that one again, we could just reload the page to try it again. We can see that now that space is being taken into account. Now as we start writing more and more code you'll often see a few blank lines. You'll often see lines indented with tabs or spaces. Again, JavaScript doesn't care. It doesn't pay attention to this. Whitespace has no actual meaning, no impact on what this code is going to do, but whitespace can be very useful for making our code more readable and we'll see much more of that soon.

Find answers to the most frequently asked questions about Foundations of Programming: Fundamentals.


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Q: Using TextEdit with Mac OS 10.9 Mavericks? 
A: If you're using the built-in TextEdit program in Mavericks to write your first examples and your code doesn't seem to be working, here's one reason why: by default, "smart quotes" are now turned on in TextEdit Preferences.
 
This is where TextEdit will automatically change pairs of double quotes to "smart quotes" - where the opening and closing quote are different, like a 66 and 99.
 
While this is fine for human eyes, programming languages don't want this - when writing code, they need to be the plain, generic straight-up-and-down quotes.
 
So make sure that in TextEdit > Preferences, that "Smart quotes" are unchecked.
 
Important! Whenever you make a change to TextEdit preferences, make sure to then completely quit out of the program (Command-Q or using TextEdit > Quit TextEdit) and then re-open it, as changes won't take effect on documents you already have open.
 
However, we're not finished - just because you've changed the preferences, it does **not** change any *existing* smart quotes back to "regular" quotes - it just doesn't add new ones - so make sure to go through your files for any time you wrote quotes and TextEdit may have changed them to smart quotes - look in both the JavaScript, and your HTML too, and compare to the downloadable exercise files if necessary.
 
If that sounds like a bit of a chore, I recommend just downloading a code editor like Sublime Text (www.sublimetext.com) or TextMate (www.macromates.com) and using that instead of TextEdit - it's only a matter of time before you'd move away from TextEdit anyway - we only used it in the course because it was built-in and a quick way to get started, but it's now become more of a inconvenience than it was before.
 
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