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

id, title, challengeType

id	title	challengeType
56533eb9ac21ba0edf2244aa	Understanding Uninitialized Variables	1

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.

Tests

tests:
  - text: <code>a</code> should be defined and evaluated to have the value of <code>6</code>
    testString: 'assert(typeof a === "number" && a === 6, "<code>a</code> should be defined and evaluated to have the value of <code>6</code>");'
  - text: <code>b</code> should be defined and evaluated to have the value of <code>15</code>
    testString: 'assert(typeof b === "number" && b === 15, "<code>b</code> should be defined and evaluated to have the value of <code>15</code>");'
  - text: <code>c</code> should not contain <code>undefined</code> and should have a value of "I am a String!"
    testString: 'assert(!/undefined/.test(c) && c === "I am a String!", "<code>c</code> should not contain <code>undefined</code> and should have a value of "I am a String!"");'
  - text: Do not change code below the line
    testString: 'assert(/a = a \+ 1;/.test(code) && /b = b \+ 5;/.test(code) && /c = c \+ " String!";/.test(code), "Do not change code below the line");'

Challenge Seed

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

// Do not change code below this line

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

After Test

console.info('after the test');

Solution

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