freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/understanding-uninitialized-variables.md

id, title, challengeType, videoUrl, forumTopicId

id	title	challengeType	videoUrl	forumTopicId
56533eb9ac21ba0edf2244aa	Understanding Uninitialized Variables	1	https://scrimba.com/c/cBa2JAL	18335

--description--

When JavaScript variables are declared, they have an initial value of undefined. If you do a mathematical operation on an undefined variable your result will be NaN which means "Not a Number". If you concatenate a string with an undefined variable, you will get a literal string of "undefined".

--instructions--

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

--hints--

a should be defined and evaluated to have the value of 6.

assert(typeof a === 'number' && a === 6);

b should be defined and evaluated to have the value of 15.

assert(typeof b === 'number' && b === 15);

c should not contain undefined and should have a value of "I am a String!"

assert(!/undefined/.test(c) && c === 'I am a String!');

You should not change code below the specified comment.

assert(
  /a = a \+ 1;/.test(code) &&
    /b = b \+ 5;/.test(code) &&
    /c = c \+ " String!";/.test(code)
);

--seed--

--after-user-code--

(function(a,b,c){ return "a = " + a + ", b = " + b + ", c = '" + c + "'"; })(a,b,c);

--seed-contents--

// Only change code below this line
var a;
var b;
var c;
// Only change code above this line

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

--solutions--

var a = 5;
var b = 10;
var c = "I am a";
a = a + 1;
b = b + 5;
c = c + " String!";