122 lines
2.6 KiB
Markdown
122 lines
2.6 KiB
Markdown
---
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id: 56533eb9ac21ba0edf2244c9
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title: Accessing Object Properties with Variables
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/cnQyKur'
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forumTopicId: 16165
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dashedName: accessing-object-properties-with-variables
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---
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# --description--
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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.
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Here is an example of using a variable to access a property:
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```js
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var dogs = {
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Fido: "Mutt", Hunter: "Doberman", Snoopie: "Beagle"
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};
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var myDog = "Hunter";
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var myBreed = dogs[myDog];
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console.log(myBreed);
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```
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The string `Doberman` would be displayed in the console.
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Another way you can use this concept is when the property's name is collected dynamically during the program execution, as follows:
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```js
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var someObj = {
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propName: "John"
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};
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function propPrefix(str) {
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var s = "prop";
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return s + str;
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}
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var someProp = propPrefix("Name");
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console.log(someObj[someProp]);
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```
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`someProp` would have a value of the string `propName`, and the string `John` would be displayed in the console.
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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*.
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# --instructions--
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Set the `playerNumber` variable to `16`. Then, use the variable to look up the player's name and assign it to `player`.
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# --hints--
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`playerNumber` should be a number
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```js
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assert(typeof playerNumber === 'number');
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```
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The variable `player` should be a string
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```js
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assert(typeof player === 'string');
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```
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The value of `player` should be the string `Montana`
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```js
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assert(player === 'Montana');
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```
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You should use bracket notation to access `testObj`
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```js
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assert(/testObj\s*?\[.*?\]/.test(code));
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```
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You should not assign the value `Montana` to the variable `player` directly.
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```js
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assert(!code.match(/player\s*=\s*"|\'\s*Montana\s*"|\'\s*;/gi));
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```
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You should be using the variable `playerNumber` in your bracket notation
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```js
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assert(/testObj\s*?\[\s*playerNumber\s*\]/.test(code));
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```
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# --seed--
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## --after-user-code--
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```js
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if(typeof player !== "undefined"){(function(v){return v;})(player);}
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```
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## --seed-contents--
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```js
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// Setup
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var testObj = {
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12: "Namath",
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16: "Montana",
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19: "Unitas"
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};
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// Only change code below this line
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var playerNumber; // Change this line
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var player = testObj; // Change this line
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```
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# --solutions--
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```js
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var testObj = {
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12: "Namath",
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16: "Montana",
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19: "Unitas"
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};
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var playerNumber = 16;
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var player = testObj[playerNumber];
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```
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