2.6 KiB
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:
var dogs = {
Fido: "Mutt", Hunter: "Doberman", Snoopie: "Beagle"
};
var myDog = "Hunter";
var 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:
var someObj = {
propName: "John"
};
function propPrefix(str) {
var s = "prop";
return s + str;
}
var 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
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];