CSCI 446 Unit #3 Part I

Preparation:

Walk through the basic JavaScript tutorials.

Sections that are not mentioned can be skipped for now, and used as a reference if needed. OR, you may want to briefly skim all the sections, just to get an idea of the language features.

• JS Introduction
• For these examples, the JS is simply embedded in onclick
• JS Where To
• As with CSS, there are multiple options for where to place JS
• What advantage is there to putting a script at the bottom of the body, rather than in the head?
• For this course, most of the JS will be in external files
• JS Output
• • Just as you can use cout statements to help debug C++ programs, in JS you can use alert and/or console.log for this purpose. These are also used extensively when learning, to see the effect of statements.
• JS Syntax
• Syntax is pretty similar to other languages
• Be sure to use camelCase for variable names
• JS Variables
• When would a variable be undefined?
• Describe two different uses for +?
• Skim JS Operators.
• Skim JS Data Types
• NOTE: JS has dynamic data types. If you've never heard that term, try putting document.writeln(x); between the assignment statements in the "Tryit" example of "JavaScript Types are Dynamic."
• Read JS Functions
• Skim the beginning of this section, which just explains what a function is (you all know that!).
• Read "The () Operator Invokes the Function" section. Of course it does. But what happens if you leave off the ()? NOTE! JS has first-class functions, which means the function itself can be returned. You have not seen first-class functions in your C++ or Java coursework, so this is a new concept. We'll return to this idea later.
• Read JS Objects
• Objects in JS are just name:pair values (basically just a hash map)
• Is it a good idea to use new to create elements like String, Number, Array?
• Skim JS Strings
• Can String objects be compared?
• Is it a good idea to access elements of a string as an array? e.g., myStr[0]
• Skim JS Numbers
• What is NaN?
• Skim JS Arrays
• What does push do?
• If there are 3 elements in array stuff, is this valid: stuff[10] = 5;? If yes, would it be good practice?
• Does JS have associative arrays (hashes)?
• How would you decide whether to store data as an array or object?
• Read JS Booleans
• Read JS Comparisons
• There are a number of aspects of JS that experienced programmers consider "bad" design. How JS does comparisons is one of them. Try these examples to see some of the pitfalls.
• Read JS Hoisting
• Are both initializations and declarations hoisted?
• What's a good practice to avoid bugs related to hoisting?
• Skim JS Strict through JS Mistakes
• These sections are important, but many of the guidelines were discussed in prior sections
• Please use camelCase for your variable names