greysonh / fewds-js-basics-arithmetic-lab-dc-fe-skills-111218

Arithmetic Lab

Assignment

It's time for your first solo assignment since joining the Flatbook team!

Here at Flatbook HQ, we're a bit overwhelmed by all of the user data we've been collecting, and we need some help crunching the numbers.

There are three challenges we need you to solve. Code your solution in index.js. We'll provide some brief instructions here, but you should really rely on the test failure messages to guide your code.

Instructions

1. When we started out, we assigned ID numbers sequentially to new users, so our first user ID is 1, second is 2, third is 3, and so on. That was fine when we were a fledgling company, but, now that we have millions of active users, it would be easier if all of our user IDs were the same length. We'd like the IDs to start from 1000000001 (one billion and one) instead of 1. Create a variable named newID that adds 1000000000 to the value in oldID. Don't define oldID — assume the system already knows what it is just by using that variable name.

2. During the sign-up process, we require new users to provide their age. However,the junior developer tasked with creating the sign-up form forgot to validate that the user had entered an integer, so we have a lot of accounts floating around with weird ages like 21.7 or 9.5. We'd like you to help us identify which users need to be prompted to reenter their age. Create a variable named ageIsValid that checks whether the value in currentAge is a valid integer. You don't have to define currentAge — the system will take care of that part.

3. Finally, we need a way to randomly select a user by their ID number. As you know, we have millions of active users, but since this is your first assignment we'll limit the testing pool to twenty users with IDs between 1000000001 and 1000000020. You're tasked with creating three variables:

• randomNumber, which should contain a randomly-generated number between 0 (inclusive) and 20 (exclusive).
• randomInteger, which should take the value in randomNumber and round it down to the nearest integer.
• randomUserID, which should convert randomInteger into a valid ID number — an integer between 1000000001 and 1000000020.

Resources

• MDN
  • Basic math in JavaScript
  • Arithmetic operators
  • Operator precedence
  • Assignment operators
  • NaN
  • Number
  • Math
• 2ality — How numbers are encoded in JavaScript

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