Multidimensional array in javasscript - javascript

I'm learning from the book JavaScript for Dummies, and from the following code, it says
console.log( bestAlbumsByGenre[0][1] ) //will output: Patsy Cline:Sentimentally Yours
var bestAlbumsByGenre = []
bestAlbumsByGenre[0] = “Country”;
bestAlbumsByGenre[0][0] = “Johnny Cash: Live at Folsom Prison”
bestAlbumsByGenre[0][1] = “Patsy Cline: Sentimentally Yours”;
bestAlbumsByGenre[0][2] = “Hank Williams: I’ m Blue Inside”;
but in the console the output is: "o". Why is that, and what am I doing wrong?

You seem to have mixed up two different exercises.
The following line is resulting in the error:
bestAlbumsByGenre[0] = "Country";
I've cleaned up the code to make it work.
However, I think I would prefer an object, where each key represents the genre, and their value is an array.
// Define the outer array
const bestAlbumsByGenre = [];
// Set the first element of the array as an array
bestAlbumsByGenre[0] = [];
// Add items to the first element (the array)
bestAlbumsByGenre[0][0] = "Johnny Cash: Live at Folsom Prison"
bestAlbumsByGenre[0][1] = "Patsy Cline: Sentimentally Yours";
bestAlbumsByGenre[0][2] = "Frank Williams: I’ m Blue Inside";
console.log(bestAlbumsByGenre[0][1]);
// Alternative approach
const reallyBestAlbumsByGenre = {
rock: [],
};
reallyBestAlbumsByGenre.rock.push("Johnny Cash: Live at Folsom Prison");
reallyBestAlbumsByGenre.rock.push("Patsy Cline: Sentimentally Yours");
reallyBestAlbumsByGenre.rock.push("Frank Williams: I’ m Blue Inside");
console.log( reallyBestAlbumsByGenre.rock[1] );

Since you want to organize albums by genre, it would make more sense to create an object with the genre as a key:
var bestAlbumsByGenre = {
"Country": [
"Johnny Cash: Live at Folsom Prison",
"Patsy Cline: Sentimentally Yours",
"Hank Williams: I’m Blue Inside",
]
}

Your not actually accessing a two dimensional array, but you are accessing the second character of a string.
Your are initializing a 1 dimensional array of string when you do:
When you did the following:
var bestAlbumsByGenre = [];
bestAlbumsByGenre[0] = "Country";
You assigned a string to the first element.
Subsequently, the other statements did nothing.
Fix
The following fixes your error:"
var bestAlbumsByGenre = [[]]
bestAlbumsByGenre[0][0] = "Country";

Related

How to get the matched values from an array to another array via (NODE.JS);

I'm new to JSCRIPT and I would like to try the twitter sentiment analysis. I have an array1 named "disectToWords" where the sentiments are located. Then, I have another array called "getScoredWords" where the "AFINN.txt" or "the scores of words" is located. I want to match both of arrays, to get the matched values. I'm trying to use filter(), however, I always got a null/empty array which means, all are false.
var getScoredWords = ['abandon',
'abandoned',
'abandons',
'abducted',
'abduction',
'abductions',
'abhor',
'abhorred',
'abhorrent',
'abhors',
'abilities',
'ability',
'aboard',
'absentee',]
var disectToWords = ['Barry',
'Manilow',
'Singin',
'With',
'The',
'Big',
'Bands',
'abducted',
'aboard',]
var result = getScoredWords.filter(words => disectToWords.includes(words));
but it should return the word 'abducted' and 'aboard'.
please help
Hello I am trying this its look fine So you can try
<script type="text/javascript">
var getScoredWords = ['abandon',
'abandoned',
'abandons',
'abducted',
'abduction',
'abductions',
'abhor',
'abhorred',
'abhorrent',
'abhors',
'abilities',
'ability',
'aboard',
'absentee',]
var disectToWords = ['Barry',
'Manilow',
'Singin',
'With',
'The',
'Big',
'Bands',
'abducted',
'aboard',]
var result = getScoredWords.filter(words => disectToWords.includes(words));
console.log(result);
</script>

How to find the position of all array items from a loop

I'm brand new to programming so I apologize if this is a simple question.
I had a unique practice problem that I'm not quite sure how to solve:
I'm dealing with two arrays, both arrays are pulled from HTML elements on the page, one array is representing a bunch of states, and the next array is representing their populations. The point of the problem is to print the name of the states and their less than average populations.
To find and print all of the populations that are less than the average I used this code:
function code6() {
// clears screen.
clr();
// both variables pull data from HTML elements with functions.
var pop = getData2();
var states = getData();
var sum = 0;
for( var i = 0; i < pop.length; i++ ){
sum += parseInt( pop[i], 10 );
var avg = sum/pop.length;
if (pop[i] < avg) {
println(pop[i]);
// other functions used in the code to get data, print, and clear the screen.
function getData() {
var dataSource = getElement("states");
var numberArray = dataSource.value.split('\n');
// Nothing to split returns ['']
if (numberArray[0].length > 0) {
return(numberArray);
} else {
return [];
}
}
// Get the data from second data column
function getData2() {
var dataSource = getElement("pops");
var numberArray = dataSource.value.split('\n');
// Nothing to split returns ['']
if (numberArray[0].length > 0) {
return(numberArray);
} else {
return [];
}
}
// Clear the 'output' text area
function clr() {
var out = getElement("output");
out.value = "";
}
// Print to the 'output' HTML element and ADDS the line break
function println(x) {
if (arguments.length === 0) x = '';
print(x + '\n');
}
Now I just need to know how to get the value of these positions within the array so I can pull out the same positions from my states array and display them both side by side. Both arrays have the identical amount of items.
I hope this makes sense and thanks in advance to anyone who has time to take a look at this.
Best regards,
-E
Its a little hard to tell what you are trying to accomplish, but I guess you are going for something like:
'use strict'
function code6() {
const populations = ['39000000', '28000000', '21000000'];
const stateNames = ['california', 'texas', 'florida'];
const states = populations.map((population, i) => ({
'name': stateNames[i],
'population': Number(population),
}));
const sum = states.reduce((sum, state) => sum + state.population, 0);
const average = sum / populations.length;
states
.filter(state => state.population < average)
.forEach(state => {
const name = state.name;
const population = state.population;
console.log(`state name: ${name}, population: ${population}`);
});
}
// run the code
code6();
// state name: texas, population: 28000000
// state name: florida, population: 21000000
I took the liberty of refactoring your code to be a little more modern (es6) and Idiomatic. I hope its not to confusing for you. Feel free to ask any questions about it.
In short you should use:
'use strict' at the top of your files
const/let
use map/filter/forEach/reduce to iterate lists.
use meaningfull names
, and you should avoid:
classic indexed for-loop
parseInt
, and pretty much never ever use:
var
If your states array is built with corresponding indices to your pop one, like this:
states; //=> ['Alabama', 'Alaska', 'Arizona', ...]
pop; //=> [4863300, 741894, 6931071, ...]
then you could simply update your print statement to take that into account:
if (pop[i] < avg) {
println(state[i] + ': ' + pop[i]);
}
Or some such.
However, working with shared indices can be a very fragile way to use data. Could you rethink your getData and getData2 functions and combine them into one that returns a structure more like this the following?
states; //=> [
// {name: 'Alabama', pop: 4863300}
// {name: 'Alaska', pop: 741894},
// {name: 'Arizona', pop: 6931071},
// ...]
This would entail changes to the code above to work with the pop property of these objects, but it's probably more robust.
If your pop and state looks like:
var state = ['state1', 'state2', ...];
var pop = ['state1 pop', 'state2 pop', ...];
Then first of all, avg is already wrong. sum's value is running along with the loop turning avg's formula into sum as of iteration / array length instead of sum of all pops / array length. You should calculate the average beforehand. array.reduce will be your friend.
var average = pop.reduce(function(sum, val){return sum + val;}, 0) / pop.length;
Now for your filter operation, you can:
Zip up both arrays to one array using array.map.
Filter the resulting array with array.filter.
Finally, loop through the resulting array using array.forEach
Here's sample code:
var states = ['Alabama', 'Alaska'];
var pop = [4863300, 741894];
var average = pop.reduce(function(sum, val){return sum + val;}) / pop.length;
console.log('Average: ' + average);
states.map(function(state, index) {
// Convert 2 arrays to an array of objects representing state info
return { name: state, population: pop[index] };
}).filter(function(stateInfo) {
console.log(stateInfo);
// Filter each item by returning true on items you want to include
return stateInfo.population < average;
}).forEach(function(stateInfo) {
// Lastly, loop through your results
console.log(stateInfo.name + ' has ' + stateInfo.population + ' people');
});

Select random item from array

I am trying to make a game for my two girls. It randomly selects an adjective and a noun, then displays the words for them to act out.
I can get the random words to print to the console, but now I need them to appear in the html.
Array.prototype.sample = function(){
return this[Math.floor(Math.random()*this.length)];
}
var randomAdj = (["happy", "sad", "bouncy", "silly"].sample());
var randNoun = (["monkey", "butterfly", "puppy"].sample());
document.getElementById(#adj).textContent = randomAdj;
document.getElementById(#noun).textContent = randomNoun;
The last two lines aren't working for me (#adj and #noun are span ids used in the html).
I am only a couple of weeks into learning, so I might be missing something super obvious here.
The random part should work (keep in mind that modifying the prototypes is not a good practice, tho), but you have two syntax errors:
document.getElementById(#adj).textContent = randomAdj;
document.getElementById(#noun).textContent = randomNoun;
Pass "adj" and "noun" as strings:
document.getElementById("adj").textContent = randomAdj;
document.getElementById("noun").textContent = randomNoun;
You don't need the # snippet in the getElementById call.
Also note that you you are using randomNoun but you declared randNoun. Here is the working code and example:
function randomItem(arr){
return arr[Math.floor(Math.random()*arr.length)];
}
var randomAdj = randomItem(["happy", "sad", "bouncy", "silly"]);
var randomNoun = randomItem(["monkey", "butterfly", "puppy"]);
document.getElementById("adj").textContent = randomAdj;
document.getElementById("noun").textContent = randomNoun;
<span id="adj"></span>
<span id="noun"></span>
worng
document.getElementById(#adj).textContent = randomAdj;
document.getElementById(#noun).textContent = randomNoun;
use
document.getElementById("adj").innerHTML = randomAdj;
document.getElementById("noun").innerHTML = randomNoun;

Search array for string - returning -1

I've been reading lots of StackOverflow answers which tell me that, in Javascript, the best way to search an array for a particular string is use indexOf(). I have been trying to make this work for a while now, and I need some help with it.
I am making a shop in a text-adventure game. These are the values I am using:
The array shopCosts:
shopCosts = [20, 25];
The array shopItems:
shopItems = [["Sword", "Shield"]];
I dynamically create radiobuttons by looping through shopItems:
for(var i = 0; i < array.length; i++)
{
// Create the list item:
var item = document.createElement('li');
// Set its contents:
item.appendChild(document.createTextNode(array[i] + " - " + shopCosts[i] + " Gold"));
// Add it to the list:
list.appendChild(item);
var label = document.createElement("label");
var radio = document.createElement("input");
var text = document.createTextNode(array[i]);
radio.type = "radio";
radio.name = "shop";
radio.value = array[i];
radio.onclick = function () { addValue(this.getAttribute("value"), shopCosts, shopItems) }
label.appendChild(radio);
label.appendChild(text);
document.body.appendChild(label);
}
This is the part in question:
radio.onclick = function () { addValue(this.getAttribute("value"), shopCosts, shopItems) }
My logic was basically to assign values to each dynamically created radiobutton, and if one was pressed, get the value (so, the name of the item you wanted to buy) and then search shopItems for that particular string for the index value. Once I had that, I would look in the same "parallel" list shopCosts to find the price.
I used console.log() to see what variables were in play. When I clicked on the radio button, this function is called:
function addValue(nameOfItem, shopCosts, shopItems)
{
var positionOfShopItem = shopItems.indexOf(nameOfItem);
console.log(positionOfShopItem);
console..log(nameOfItem);
console.log(shopItems);
}
Surely, the console.log() would return the position of the named item? To prove to myself I'm not going crazy, here's what the Dev Tools say:
-1
Sword
[Array[2]]
0: "Sword"
1: "Shield"
Sword is clearly in the array, in position 0, so why is indexOf() returning -1?
Any help appreciated!
As I alluded to in my comment, its because shopItems does not contain an array of strings, it contains a single element, where that one element is an array of strings. I suspect your code would work just fine if you removed the extra square braces
var shopItems = ["Sword", "Shield"];
I realize you've already fixed the bug, but I urge you to consider a different approach to the problem. These two principles will not only solve the problem in a cleaner way, but they also give you a new way to think about similar problems in the future:
Never use parallel arrays. Use a single array of objects instead.
In your main loop that appends the items, put the main body of the loop in a function.
If you follow these two ideas you gain several benefits. The code becomes much more straightforward, easier to maintain, and you don't have to do any array lookups at all!
Each shop item is packaged up as a single object in the array, like this:
var shopItems = [
{ name: 'Sword', cost: 20 },
{ name: 'Shield', cost: 25 }
];
So if you have a reference to the shop item as a whole, say in a variable called shopItem, then you automatically have all of its properties available: shopItem.name and shopItem.cost. This lets you also easily add more bits of data to a shop item, e.g.
var shopItems = [
{ name: 'Sword', cost: 20, dangerous: true },
{ name: 'Shield', cost: 25, dangerous: false }
];
and now shopItem.dangerous will give you the appropriate value. All without any array lookups.
Making the main loop body into a function adds a further benefit: Inside that function, its parameters and local variables are preserved each time you call the function (this is called a closure). So now you don't even have to fetch the list item value and look it up - you already have the appropriate shopItem available in the code.
Putting this together, the code might look like this:
var shopItems = [
{ name: 'Sword', cost: 20, dangerous: true },
{ name: 'Shield', cost: 25, dangerous: false }
];
var list = document.getElementById( 'list' );
for( var i = 0; i < shopItems.length; ++i ) {
appendShopItem( shopItems[i] );
}
// Alternatively, you could use .forEach() instead of the for loop.
// This will work in all browsers except very old versions of IE:
// shopItems.forEach( appendShopItem );
function appendShopItem( shopItem ) {
// Create the list item:
var item = document.createElement( 'li' );
// Set its contents:
item.appendChild( document.createTextNode(
shopItem.name + ' - ' + shopItem.cost + ' Gold'
) );
// Add it to the list:
list.appendChild( item );
var label = document.createElement( 'label' );
var radio = document.createElement( 'input' );
var text = document.createTextNode( shopItem.name );
radio.type = 'radio';
radio.name = 'shop';
radio.value = shopItem.name;
radio.onclick = function () {
addValue( shopItem );
};
label.appendChild( radio );
label.appendChild( text );
document.body.appendChild( label );
}
function addValue( shopItem ) {
console.log( shopItem );
alert(
shopItem.name +
' costs ' + shopItem.cost + ' and is ' +
( shopItem.dangerous ? 'dangerous' : 'not dangerous' )
);
}
New fiddle (with a tip of the hat to Jamiec for the original fiddle)
As you can see, this makes the code much easier to understand. If you have a shopItem, you automatically have its name, cost, and any other property you want to add. And most importantly, you never have to keep track of putting your values in the same order in two, three, or even more different arrays.
shopItems is an Array of Arrays. The 0 index of shopItems contains another array which contains:
["Sword", "Shield"]
So when you are trying to find the "Sword" item or "Shield" Item inside of shopItems it is returning -1 because it cannot find either inside of the array.
Change
shopItems = [["Sword", "Shield"]];
To
shopItems = ["Sword", "Shield"];
And that will fix your issue.
I've fixed it!
Removing the double square brackets resulted in this mess. So, as a workaround, I simply added [0] to var positionOfShopItem = shopItems.indexOf(nameOfItem); to get var positionOfShopItem = shopItems[0].indexOf(nameOfItem);
Thanks for everyone's help.

Add objects to JSON

I have a JSON that looks like this:
{
"__v":0,
"_id":"526a7b9c1affd1401d000001",
"ranStr":"azsuC2Ers0qTEcpzS8Jrs1pZ7MQH0goa",
"userId":{
"username":"t",
"_id":"51e11b28418dcfd01f000002"
},
"meta":{
"numberComments":0,
"favs":0,
"views":112
},
"enddate":"2014-01-31T00:00:00.000Z",
"startdate":"2013-10-25T00:00:00.000Z",
"comments":[],
"categories":[],
"fileurl":[],
"telephone":"1234567890"
}
When I add an object to it:
addObj[obj.length] = saveobject;
the previous content gehts replaced.
When I make an array out of it and push the object:
addObj = [loadedJSON];
addObj.push(saveObj);
I get this after the first
[Object]
after the second so fare so good
[Object, Object]
and after the third it gets messed up
[Array(2), Object]
What do I miss?
I hope some one can help with this?
The way I hoped it would look like is this.
[Object, Object, Object, ...and so on]
EDIT
to be More specific
when I add a new Object I load the JSON file in a variable and then I try to add the new Object.
Which works for the first two objects but the third one is added to the first object so that I got this result.
[Array(2), Object]
I dont want it nested like this! But how do I get it like this?
[Object, Object, Object].
EDIT
So eventually you all were right I just mixed up the array when i loaded it the second time every thing is fine now thank for pointing me in the right direction.
on the first time:
var a= [];
var b= {};
b= 'some things';
a.push(b);
and wenn a.length != null
b= 'the rest';
a.push(b);
and now everything is just as expected!
As far as I understand it, this has nothing to do with JSON.
It seems you want to have an array storing successive instances of a given object (that happens to have been encoded in JSON at some point, but for the problem at hand we could not care less).
First, create a sorage array.
Then push each new instance into it.
var storage = []; // your storage array, initially empty
// ....
while (some_guy_wants_to_send_me_something ())
{
var new_object = get_what_the_guy_sent_me_that_happens_to_be_JSON_encoded();
storage.push (new_object);
}
EDIT:
If you use a button:
var storage = []; // your storage array, initially empty
// ....
function add_whatever_object ()
{
var new_object = get_what_the_guy_sent_me_that_happens_to_be_JSON_encoded();
storage.push (new_object);
}
// HTML
<button type="button" onclick='add_whatever_object();'>
I still don't see where the catch is.
check the if it is an array:
Array.isArray(loadedJSON) //true
do this:
loadedJSON.push(saveObj);
if it was not an array push it to an array:
var myarray = [];
myarray.push(loadedJSON);
an then push your other object:
myarray.push(saveObj);
an so on:
myarray.push(otherObj);
I am a little unclear on what you actually want, but based on a little speculation I was able to write the following code for you. I hope this will solve your problem.
var a ={
"__v":0,
"_id":"526a7b9c1affd1401d000001",
"ranStr":"azsuC2Ers0qTEcpzS8Jrs1pZ7MQH0goa",
"userId":{
"username":"t",
"_id":"51e11b28418dcfd01f000002"
},
"meta":{
"numberComments":0,
"favs":0,
"views":112
},
"enddate":"2014-01-31T00:00:00.000Z",
"startdate":"2013-10-25T00:00:00.000Z",
"comments":[],
"categories":[],
"fileurl":[],
"telephone":"1234567890"
};
var b ={
"__v":0,
"_id":"526a7b9c1affd1401d000001",
"ranStr":"azsuC2Ers0qTEcpzS8Jrs1pZ7MQH0goa",
"userId":{
"username":"t",
"_id":"51e11b28418dcfd01f000002"
},
"meta":{
"numberComments":0,
"favs":0,
"views":112
},
"enddate":"2014-01-31T00:00:00.000Z",
"startdate":"2013-10-25T00:00:00.000Z",
"comments":[],
"categories":[],
"fileurl":[],
"telephone":"1234567890"
};
var c ={
"__v":0,
"_id":"526a7b9c1affd1401d000001",
"ranStr":"azsuC2Ers0qTEcpzS8Jrs1pZ7MQH0goa",
"userId":{
"username":"t",
"_id":"51e11b28418dcfd01f000002"
},
"meta":{
"numberComments":0,
"favs":0,
"views":112
},
"enddate":"2014-01-31T00:00:00.000Z",
"startdate":"2013-10-25T00:00:00.000Z",
"comments":[],
"categories":[],
"fileurl":[],
"telephone":"1234567890"
};
var ObjArr = [];
ObjArr.push(a);
ObjArr.push(b);
ObjArr.push(c);
console.log(ObjArr);
Here is the fiddle to it => http://jsfiddle.net/rB3Un/

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