CPNT 262 Day 7 - Validating value types, Scope and Review

Housekeeping

• Assignment 1 now due Sunday Oct 17 @ 11:59pm
• Assignment 2 announced

Trophy of the day

• Text area character counter

1. Spoiler demo: Tip calculator upgrade

• Tip Calculator with drop down menu

2. Value validation

A common task in untyped languages is confirming the value type that you're working with.

Materials

• Takeaways: Validating values

Activity

• Using your knowledge of comparison operators and conditional statements, add validation to your Tip Calculator that ensures that:
  1. Remove the required attribute from total field so we can test;
  2. The user entered a number for Bill Total (i.e. not empty);
  3. The entered Bill Total is greater than $0;
  4. Throw an error if total is negative or missing.

3. Scope

Materials

• Article: A Simple Explanation of Scope in JavaScript
• Scope terminology

4. Activity: Text area counter

Materials

• <textarea> HTML Element
• Element.getAttribute()

Activity

• Text area character counter

Lab Time

• Walkthrough of this week's in-class code

Prep

Validating value types

• Takeaways: Validating values

Scope

• Article: A Simple Explanation of Scope in JavaScript
• Video: Javascript the Weird Parts: Function scope and the execution stack @59:58 (you can stop at Dynamic Typing)
• StackOverflow: Do DOM tree elements with ids become global variables?

Forms

• <textarea> HTML Element