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

id, title, challengeType, videoUrl, forumTopicId, dashedName

id	title	challengeType	videoUrl	forumTopicId	dashedName
56533eb9ac21ba0edf2244c9	Accessing Object Properties with Variables	1	https://scrimba.com/c/cnQyKur	16165	accessing-object-properties-with-variables

--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:

const dogs = {
  Fido: "Mutt",
  Hunter: "Doberman",
  Snoopie: "Beagle"
};

const myDog = "Hunter";
const myBreed = dogs[myDog];
console.log(myBreed);

The string Doberman would be displayed in the console.

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

const someObj = {
  propName: "John"
};

function propPrefix(str) {
  const s = "prop";
  return s + str;
}

const someProp = propPrefix("Name");
console.log(someObj[someProp]);

someProp would have a value of the string propName, and the string John would be displayed in the console.

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 the string 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
const testObj = {
  12: "Namath",
  16: "Montana",
  19: "Unitas"
};

// Only change code below this line
const playerNumber = 42;  // Change this line
const player = testObj;   // Change this line

--solutions--

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