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Foundations of Programming: Fundamentals
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Working with complex conditions


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Foundations of Programming: Fundamentals

with Simon Allardice

Video: Working with complex conditions

So I am going to create a condition and then add a little more thought to it. In this JavaScript file, I am starting off by creating a variable called balance, setting it equal to 5000, just to give us something to work with. Then I'm going to write my if statement. The condition, I am going to write here will be if balance is greater than 0, Yes, we know it is, but we are just writing some sample code. Then I need my code block. Now, it's very common that you'll see programmers when they hit the opening curly brace to also then jump a couple of lines, and do the closing curly brace.
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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

Working with complex conditions

So I am going to create a condition and then add a little more thought to it. In this JavaScript file, I am starting off by creating a variable called balance, setting it equal to 5000, just to give us something to work with. Then I'm going to write my if statement. The condition, I am going to write here will be if balance is greater than 0, Yes, we know it is, but we are just writing some sample code. Then I need my code block. Now, it's very common that you'll see programmers when they hit the opening curly brace to also then jump a couple of lines, and do the closing curly brace.

And this just verifies that I have both of them in place and I'll just come back up and start typing the code that's indented inside my code block. So we are just trying to prove a point here. So I'll do something like alert, the balance is positive, and we have a very straightforward condition. But the question is well, what if it's not? What if that was false? I could do another if statement and check balance again, but what I could also do instead is if that's not the case, I am going to add the word else.

Then I'm going to do the opening curly brace for the code block again because I wrote that, do the closing one, and what we have going on is if the condition is true, we'll do whatever is in the first code block. Otherwise or else, we'll do whatever is in the second code block. So I'm going to write a line of code here, closing that with a semicolon. Now, I have introduced a very common error here and it's an error in my thinking, not in the code.

We ask if balance is greater than 0, we're going to output a message saying the balance is positive. Otherwise, we'll output a message saying the balance is negative. Well, what happens if it's 0? In this case, we're going to hit the if statement. If balance is greater than 0, well that would be false. So if our balance is 0, it will give us the balance is negative message. really not what we want, but it's quite a common error to get hit with, particularly when you're dealing with things like positive and negative numbers. So be a bit too exclusive about what you're checking against.

Thinking a bit deeper about it, what I want to ask here is if the balance is greater than or equal to 0. And of course what we are asking there is as far as our program is concerned, what do we care about? Let's say we are dealing with bank balances, where 0 would not count as a negative balance. Now, there is an operator for that. It's just the greater than or equals sign. This is regarded as a single operator. So it's just the two characters next to each other. What we can also do is take this a little bit further.

Inside this first code block that will be executed if the balance is greater than or equal to 0, I could add another if statement. If balance is greater than 10,000, do my opening curly brace for the code block, couple of lines, and then do the closing one. And notice that what I am doing here is trying to make this apparent. I am lining up my closing curly brace with its corresponding if statement, the same way that I would line up the first closing curly brace with its corresponding if statement, and then I would indent any code inside of that.

If I were to save this and then jump over to my container HTML page that will run it, we should get The balance is positive. Click OK. But we do not get this internal if statement because balance is not greater than 10,000. That would be false. So you can create multiple levels of complex conditions inside your code. Now, do be aware, don't nest too deep. JavaScript can handle a thousand levels of If statements if you started to type them, but lots of nested Ifs, say beyond three levels, can get very difficult to read and make sense of just for a human being.

If we do have to have more complex logic, there are other techniques we can use to deal with it, such as working with functions which we're going to get to 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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