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freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/accessing-object-properties-with-variables.md
Kristofer Koishigawa bcc9beff1f feat(curriculum): introduce let and const earlier (#43133)
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---
id: 56533eb9ac21ba0edf2244c9
title: Accessing Object Properties with Variables
challengeType: 1
videoUrl: 'https://scrimba.com/c/cnQyKur'
forumTopicId: 16165
dashedName: 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:
```js
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:
```js
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
```js
assert(typeof playerNumber === 'number');
```
The variable `player` should be a string
```js
assert(typeof player === 'string');
```
The value of `player` should be the string `Montana`
```js
assert(player === 'Montana');
```
You should use bracket notation to access `testObj`
```js
assert(/testObj\s*?\[.*?\]/.test(code));
```
You should not assign the value `Montana` to the variable `player` directly.
```js
assert(!code.match(/player\s*=\s*"|\'\s*Montana\s*"|\'\s*;/gi));
```
You should be using the variable `playerNumber` in your bracket notation
```js
assert(/testObj\s*?\[\s*playerNumber\s*\]/.test(code));
```
# --seed--
## --after-user-code--
```js
if(typeof player !== "undefined"){(function(v){return v;})(player);}
```
## --seed-contents--
```js
// Setup
const testObj = {
12: "Namath",
16: "Montana",
19: "Unitas"
};
// Only change code below this line
const playerNumber; // Change this line
const player = testObj; // Change this line
```
# --solutions--
```js
const testObj = {
12: "Namath",
16: "Montana",
19: "Unitas"
};
const playerNumber = 16;
const player = testObj[playerNumber];
```