* fix: move "Explore Differences Between..." to basic JS, update seed and tests * fix: resequence "Declare String Variables" * fix: move "Declare a Read-Only Variable..." to basic JS, update seed and tests * fix: revert changes to non-English "Explore Differences Between..." test text * fix: revert test strings, solutions, and seeds for non-English challenges * fix: update "Declare String Variables" description * fix: sync quotation marks in description and seed * fix: modify note in "Declare a Read-Only..." challenge * fix: update operator and compound assignment challenges * fix: update string challenges * fix: update array and array method challenges * fix: update function and scope challenges, resequence slightly * fix: "Word Blanks" solution * fix: add spacing to seed * fix: concatenating += challenge spacing * fix: appending variables to strings spacing * fix: find the length of a string spacing * fix: removed instances of removedFromMyArray = 0 * fix: switch challenges * fix: function argument and param spacing * fix: update counting cards, object challenges, and record collection * fix: finish rest of Basic JS section * fix: introducing else statements solution * fix: update spacing and wording * fix: update wording for const challenge * fix: update functional programming challenges * fix: intermediate algorithms and cert challenges * fix: revert some spacing and remove comments for fp challenge solutions * feat: add notes with links to moved let and const challenges in first two es6 challenges * fix: update es6 intro text * Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/concatenating-strings-with-the-plus-equals-operator.md Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/finding-a-remainder-in-javascript.md Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/global-scope-and-functions.md Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/iterate-through-an-array-with-a-for-loop.md Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/iterate-through-an-array-with-a-for-loop.md Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/functional-programming/implement-map-on-a-prototype.md Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * Update curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-javascript/declare-a-read-only-variable-with-the-const-keyword.md Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * fix: concatenating strings with plus operator seed * fix: add comments back to Declare a Read-Only Variable... seed * feat: add es6 to basic javascript redirect tests for let and const challenges * fix: revert "Concatenating Strings with Plus Operator" seed * fix: move test file to cypress/integration/learn/redirects, separate redirect tests Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>
126 lines
2.6 KiB
Markdown
126 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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const dogs = {
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Fido: "Mutt",
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Hunter: "Doberman",
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Snoopie: "Beagle"
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};
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const myDog = "Hunter";
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const 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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const someObj = {
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propName: "John"
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};
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function propPrefix(str) {
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const s = "prop";
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return s + str;
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}
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const 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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const 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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const playerNumber; // Change this line
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const player = testObj; // Change this line
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```
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# --solutions--
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```js
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const 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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const playerNumber = 16;
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const player = testObj[playerNumber];
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```
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