freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/accessing-object-properties-with-variables.md

id, title, challengeType, videoUrl, forumTopicId

id	title	challengeType	videoUrl	forumTopicId
56533eb9ac21ba0edf2244c9	Accessing Object Properties with Variables	1	https://scrimba.com/c/cnQyKur	16165

--description--

Another use of bracket notation on objects is to access a property which is stored as the value of a variable. This can be very useful for iterating through an object's properties or when accessing a lookup table.

Here is an example of using a variable to access a property:

var dogs = {
  Fido: "Mutt",  Hunter: "Doberman",  Snoopie: "Beagle"
};
var myDog = "Hunter";
var myBreed = dogs[myDog];
console.log(myBreed); // "Doberman"

Another way you can use this concept is when the property's name is collected dynamically during the program execution, as follows:

var someObj = {
  propName: "John"
};
function propPrefix(str) {
  var s = "prop";
  return s + str;
}
var someProp = propPrefix("Name"); // someProp now holds the value 'propName'
console.log(someObj[someProp]); // "John"

Note that we do not use quotes around the variable name when using it to access the property because we are using the value of the variable, not the name.

--instructions--

Set the playerNumber variable to 16. Then, use the variable to look up the player's name and assign it to player.

--hints--

playerNumber should be a number

assert(typeof playerNumber === 'number');

The variable player should be a string

assert(typeof player === 'string');

The value of player should be "Montana"

assert(player === 'Montana');

You should use bracket notation to access testObj

assert(/testObj\s*?\[.*?\]/.test(code));

You should not assign the value Montana to the variable player directly.

assert(!code.match(/player\s*=\s*"|\'\s*Montana\s*"|\'\s*;/gi));

You should be using the variable playerNumber in your bracket notation

assert(/testObj\s*?\[\s*playerNumber\s*\]/.test(code));

--seed--

--after-user-code--

if(typeof player !== "undefined"){(function(v){return v;})(player);}

--seed-contents--

// Setup
var testObj = {
  12: "Namath",
  16: "Montana",
  19: "Unitas"
};

// Only change code below this line

var playerNumber;       // Change this line
var player = testObj;   // Change this line

--solutions--

var testObj = {
  12: "Namath",
  16: "Montana",
  19: "Unitas"
};
var playerNumber = 16;
var player = testObj[playerNumber];