Understandung the Understanding Uninitialized Variables

JavaScript
1

My code passed, but I have no idea why or what I was to get out of this. My code has asterisks.

Tell us what’s happening:

Your code so far

// Initialize these three variables
var a;
var b;
var c;

// Do not change code below this line

* a = 5;
* b = 10;
* var c = "I am a";

* a = a + 1;
* b = b + 5;
* c = c + " String!";

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0.

Link to the challenge:
https://www.freecodecamp.org/challenges/understanding-uninitialized-variables

2

What don’t you understand. For example, the instructions say:

Initialize the three variables a, b, and c with 5, 10, and "I am a" respectively so that they will not be undefined.

If you initialize a to 5, then a = a + 1 evaluates to 6, meeting the test, “a should be defined and have a value of 6”.

Is it the idea of initializing that is confusing you? Is it the math of how a ends up being 6?

3

You may be overthinking this one.

The challenge was attempting to drive home the idea that uninitialized variables cause unexpected results so be sure to init your variables.

var a;
var b = 10;

var c = b + 2;  //works, now c is 12

var d = a + 2; //d is NaN - you're not getting an expected result in d

Getting a result like NaN or “undefined” is actually a good thing in that at least your mistake is then obvious.

Sometimes not initializing a variable is not so obvious though.
Don’t do this - it is infinite loop so will crash your browser.

var i;
while(i != 100){  //sloppy test
   //do some stuff
   i++;
}