CPNT 262 Day 16 - Express JSON routes

Housekeeping

• Assignment 5: Deployed REST API

Trophy of the Day

• A REST API with the endpoints:

  GET /api/your-object-here
  GET /api/your-object-here/:id

1. Higher order functions with array.find()

Terminology

Higher order function

A function that hides (abstracts) information so we can tackle a problem at a higher (more abstract level). Examples: Array.forEach(), Array.filter(), Array.find().

Materials

• Search: "js higher order functions"
• Reference
  • Array.prototype.find()
• Gists:
  • Find a value in an array
  • Find an object in an array

Key Takeaways

• Array.find() loops through an array of objects and expects a Boolean return value:
  • If true is returned, the loop stops and Array.find() returns the current item;
  • If false is returned, the loop continues to the next item;
  • If no items are found by the end of the loop, Array.find() returns undefined.
• This method is considered a higher order function, meaning it hides (abstracts) information so we can tackle a problem at a higher (more abstract level). In this case, Array.find() hides the fact that it's looping through the array (and that it operations differently based on a boolean result).

Activity: Practice with Array.find()

1. Find your array from your Gallery .forEach() assignment (or some other array of Objects);
2. Choose a property (with a string or number value) within your objects to test against;
3. Using process.argv and Array.find(), create a command line app that returns the item that matches the inputValue that is passed from the command line OR print a "Please try again" statement if no items were found.

2. Express routes

Materials

• Prep
  • Review:
    • How to build a REST API with Node js & Express by Programming with Mosh
    • Introduction to REST
  • Express Routes in the ExpressJS Documentation
• Sample Code
  • Guild starter code

3. Route parameters and request.params

Materials

• Prep
  • Route parameters (linked to "Route parameters" section of "Express Routes" above)
  • Step 3 - Using req.params with Routes in How To Retrieve URL and POST Parameters with Express on Digital Ocean
  • Reference: req.params
• Sample code
  • Definitions in-class code

Activity

• Express Activity: Create a JSON endpoint using route parameters