Review: JavaScript 2

1. Prep

Before proceeding, be sure you’ve completed Studio: JavaScript 2).

2. Summary

Slides

Note: The video focuses on concepts from the Studio, but you are expected to be comfortable with the contents of all the prep material, which included more in-depth and broad coverage of JavaScript’s Objects.

3. References (optional)

• JSDOM: The example source code for a JavaScript-based DOM.
• First-Class Functions allow for another paradigm, functional programming. Functional programming provides another unique, different way to think about computation and, like the other paradigms, can often be a valuable tool to simplify complex work. OpenSource.com’s An introduction to functional programming in JavaScript (there are many other great examples too). Here are a few brief, silly examples:

  var a = ["Hi", "Bye", "this", "that", "pop"]  
  // Print each item in the array
  a.forEach(function(a) { console.log(a); } )
  // Find the total number of letters of all words
  a.reduce(function(accumulator, item) { return accumulator+item.length; }, 0)
  // Make a new array with each word doubled (I.e., Hi becomes HiHi)
  a.map(function(item) { return item+item; })
  // Remove words that start with t
  a.filter(function(item) { return item[0]!='t'; })
  

  In general:

  • forEach can be used to apply an operation to each element of the array.
  • reduce can be used to find a single “result” from the array
  • map can be used to create a new array based on the existing array
  • filter can be used to remove unwanted elements that match a pattern