Develop Reference

Map.delete() not working on key in parent Map

What I'm doing right now, is deleting any diff that doesn't contain the string, and if the diff's dictionary is empty, then i try to delete the map.
the issue here is that, i can't delete a map with data.delete(map) for some reasons (no errors in console) and any piece of code located after that deletion in the if statement won't run.
here is the code in question:
var data = new Map({"593620 Linked Horizon - Shinzou o Sasageyo! [TV Size]": {"difficulties": {"Titan": 86813}}, "859608 LiSA - ADAMAS (TV Size)": {"difficulties": {"Kibbleru's Blue Rose": 899}},"940746 CHiCO with HoneyWorks - Kimi ga Sora Koso Kanashikere": {"difficulties": {"Taeyang's Extra": 72321}}});
var string = "titan";
Array.from(data.keys()).forEach(function(map) {
if (!(map.toLowerCase().indexOf(string.toLowerCase()) >=0)) {
if (document.getElementById("diff_search_box").checked) {
Array.from(data.get(map).get("difficulties").keys()).forEach(function(diff) {
if (!(diff.toLowerCase().indexOf(string) >= 0)) {
data.get(map).get("difficulties").delete(diff)
}
})
if (Array.from(data.get(map).get("difficulties").keys()).length = 0) {
data.delete(map)
}
}
}
})
in this situation, I'm supposed to get a dictionary such as:
{
"593620 Linked Horizon - Shinzou o Sasageyo! [TV Size]": {
"difficulties": {"Titan": 86813}
}
}

Huge number of problems with this code. My recommendation is don't write so much code without running it to make sure it works first. Write small pieces at a time and run it as you go making sure everything works along the way.
Issue number one is you cannot initialize a map with an object like that. The Map must be initialized with an array of arrays that are each two elements long, each containing the key value pairs for the map. You can fix this by wrapping the object in Object.entries() as that will return the key vale pairs for the object.
Second problem is titan is a string so it should be "titan".
Number three, you're calling .get on an object in the line data.get(map).get("difficulties"). Objects do not have .get, you have to use brackets or dot syntax: data.get(map).difficulties or data.get(map).difficulties.
Fourth, I think you don't actually want to delete the data from the map. If you did, when the user changes the search text the old data would still be gone.
Why are you using map anyways? you can simply use a normal object.
Just do this if you must use maps:
var data = new Map(Object.entries({
"593620 Linked Horizon - Shinzou o Sasageyo! [TV Size]": {
"difficulties": {"Titan": 86813}
},
"859608 LiSA - ADAMAS (TV Size)": {
"difficulties": {"Kibbleru's Blue Rose": 899}
},
"940746 CHiCO with HoneyWorks - Kimi ga Sora Koso Kanashikere": {
"difficulties": {"Taeyang's Extra": 72321}
}
}));
var string = 'titan';
function search(s) {
var r = {};
for( const [key, value] of data ) {
for( const diffKey in value.difficulties ) {
if(diffKey.toLowerCase().indexOf(string) != -1)
r[key] = value;
}
}
return new Map(Object.entries(r));
}
With this function, you can do search(string) and it will return you the map that you were wanting originally.
Mainly you should writing a bunch of code without running anything.

Map needs an iterable like an array passed to it such as:
new Map([['Key 1', 'Value 1'], ['Key 1', 'Value 1']])
You can't pass an object literal to it but you can easily use Object.entries() to extract the needed array from your object.
Then you can use Map.prototype.forEach() to loop over all the Map entries
var data = {"593620 Linked Horizon - Shinzou o Sasageyo! [TV Size]": {"difficulties": {"Titan": 86813}}, "859608 LiSA - ADAMAS (TV Size)": {"difficulties": {"Kibbleru's Blue Rose": 899}},"940746 CHiCO with HoneyWorks - Kimi ga Sora Koso Kanashikere": {"difficulties": {"Taeyang's Extra": 72321}}};
const map = new Map(Object.entries(data));
map.forEach((value, key) =>{
const {difficulties} = value;
console.log('Map key:', key.toLowerCase());
// if(someCondition){
// map.delete(key)
// }
Object.entries(difficulties).forEach(([k,v])=>{
console.log('Diff key:', k, ' Diff value:', v)
// if(k.toLowerCase().includes('titan')){
// delete difficulties[key];
// }
})
console.log('*****************************')
})

surprising to see none of the previous answer saw that, another person on a discord server i do support for software stuff on pointed out the last if condition and the fact it's missing a = so it appear as
if (Array.from(data.get(map).get("difficulties").keys()).length == 0) {
// was = before, == now
data.delete(map)
}
so now i indeed obtain a data dictionary with only 1 element containing the map which also have the difficulty that's contained in the specified string.

Preventing duplicate objects from being added to array?

I am building a little shop for a client and storing the information as an array of objects. But I want to ensure that I am not creating "duplicate" objects. I have seen similar solutions, but perhaps it is my "newness" to coding preventing me from getting the gist of them to implement in my own code, so I'd like some advice specific to what I have done.
I have tried putting my code in an if look, and if no "part", my variable looking for part number, exists in the code, then add the part, and could not get it to function.
Here is the function I am working on:
function submitButton(something) {
window.scroll(0, 0);
cartData = ($(this).attr("data").split(','));
arrObj.push({
part: cartData[0],
description: cartData[1]
});
}
arrObj is defined as a global variable, and is what I am working with here, with a "part" and a "description", which is the data I am trying to save from elsewhere and output to my "#cart". I have that part working, I just want to ensure that the user cannot add the same item twice. (or more times.)
Sorry if my code is shoddy or I look ignorant; I am currently a student trying to figure these things out so most of JS and Jquery is completely new to me. Thank you.

You can create a proxy and use Map to hold and access values, something like this
let cart = new Map([{ id: 1, title: "Dog toy" }, { id: 2, title: "Best of Stackoverflow 2018" }].map(v=>[v.id,v]));
let handler = {
set: function(target,prop, value, reciver){
if(target.has(+prop)){
console.log('already available')
} else{
target.set(prop,value)
}
},
get: function(target,prop){
return target.get(prop)
}
}
let proxied = new Proxy(cart, handler)
proxied['1'] = {id:1,title:'Dog toy'}
proxied['3'] = {id:3,title:'Dog toy new value'}
console.log(proxied['3'])

Assuming the 'part' property is unique on every cartData, I did checking only based on it.
function submitButton(something) {
window.scroll(0, 0);
cartData = ($(this).attr("data").split(','));
if(!isDuplicate(cartData))
arrObj.push({
part: cartData[0],
description: cartData[1]
});
}
const isDuplicate = (arr) => {
for(obj of arrObj){
if(arr[0] === obj.part)
return true;
}
return false;
}
If you want to do the checking on both 'part' and 'description' properties, you may replace the if statement with if(arr[0] === obj.part && arr[1] === obj.description).

Thanks everyone for their suggestions. Using this and help from a friend, this is the solution that worked:
function submitButton(something) {
window.scroll(0,0);
cartData = ($(this).attr("data").split(','));
let cartObj = {
part: cartData[0],
description: cartData[1],
quantity: 1
}
match = false
arrObj.forEach(function(cartObject){
if (cartObject.part == cartData[0]) {
match = true;
}
})
console.log(arrObj);
if (!match) {
arrObj.push(cartObj);
}

Okay, you have multiple possible approaches to this. All of them need you to specify some kind of identifier on the items which the user can add. Usually, this is just an ID integer.
So, if you have that integer you can do the following check to make sure it's not in the array of objects:
let cart = [{ id: 1, title: "Dog toy" }, { id: 2, title: "Best of Stackoverflow 2018" }];
function isInCart(id) {
return cart.some(obj => obj.id === id);
}
console.log(isInCart(1));
console.log(isInCart(3));
Another approach is saving the items by their id in an object:
let cart = { 1: { title: "Dog toy" }, 2: { title: "Best of Stackoverflow 2018" } };
function isInCart(id) {
if(cart[id]) return true;
return false;
}

Try to use indexOf to check if the object exists, for example:
var beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];
console.log(beasts.indexOf('aaa'));
// expected output: -1

How to convert arrays to objects in javascript?

How could I rewrite this code to object javascript. Since Array usage is prohibed, I can only use objects here. Insted of pushing values to array, I would like to push this values into objects.
var container = [];
document.addEventListener("submit", function(e){
e.preventDefault();
});
window.addEventListener("load",function(){
var submit = document.getElementsByClassName("btn-primary");
submit[0].addEventListener("click",add,false);
document.getElementById("pobrisi").addEventListener("click",deleteAll,false);
var dateElement = document.getElementById('datum');
dateElement.valueAsDate = new Date();
var today = new Date();
var dd = today.getDate();
var mm = today.getMonth()+1;
var yyyy = today.getFullYear();
if(dd<10){
dd='0'+dd
}
if(mm<10){
mm='0'+mm
}
today = yyyy+'-'+mm+'-'+dd;
dateElement.setAttribute("min",today);
});
function add() {
var title = document.getElementById("title").value;
var type = document.getElementById("type").value;
var datum = document.getElementById("datum").value.split("-");
datum = datum[2]+". "+datum[1]+". "+datum[0];
var data = new Book(title,type,datum);
container.push(data.add());
display();
}
function display(data) {
var destination = document.getElementById("list");
var html = "";
for(var i =0;i <container.length; i++) {
html +="<li>"+container[i]+"</li>";
}
destination.innerHTML = html;
}
function deleteAll(){
container=[];
document.getElementById("list").innerHTML="";
}
Wondering if is possible to write this code whitout any array usage.

initial remarks
The problem here, in my estimation, is that you haven't learned the fundamentals of data abstraction yet. If you don't know how to implement an array, you probably shouldn't be depending on one quite yet. Objects and Arrays are so widespread because they're so commonly useful. However, if you don't know what a specific data type is affording you (ie, what convenience does it provide?), then it's probable you will be misusing the type
If you take the code here but techniques like this weren't covered in your class, it will be obvious that you received help from an outside source. Assuming the teacher has a curriculum organized in a sane fashion, you should be able to solve problems based on the material you've already covered.
Based on your code, it's evident you really have tried much, but why do you think that people here will come up with an answer that your teacher will accept? How are we supposed to know what you can use?
a fun exercise nonetheless
OK, so (we think) we need an Array, but let's pretend Arrays don't exist. If we could get this code working below, we might not exactly have an Array, but we'd have something that works like an array.
Most importantly, if we could get this code working below, we'd know what it takes to make a data type that can hold a dynamic number of values. Only then can we begin to truly appreciate what Array is doing for us.
// make a list
let l = list(1) // (1)
// push an item on the end
l = push(l, 2) // (1 2)
// push another item on the end
l = push(l, 3) // (1 2 3)
// display each item of the list
listeach(l, function (x) {
console.log(x)
})
// should output
// 1
// 2
// 3
runnable demo
All we have to do is make that bit of code (above) work without using any arrays. I'll restrict myself even further and only use functions, if/else, and equality test ===. I see these things in your code, so I'm assuming it's OK for me to use them too.
But am I supposed to believe your teacher would let you write code like this? It works, of course, but I don't think it brings you any closer to your answer
var empty = function () {}
function isEmpty (x) {
return x === empty
}
function pair (x,y) {
return function (p) {
return p(x,y)
}
}
function head (p) {
return p(function (x,y) {
return x
})
}
function tail (p) {
return p(function (x,y) {
return y
})
}
function push (l, x) {
if (isEmpty(l))
return list(x)
else
return pair(head(l), push(tail(l), x))
}
function list (x) {
return pair(x, empty)
}
function listeach (l, f) {
if (isEmpty(l))
return null
else
(f(head(l)), listeach(tail(l), f))
}
// make a list
let l = list(1) // (1)
// push an item on the end
l = push(l, 2) // (1 2)
// push another item on the end
l = push(l, 3) // (1 2 3)
// display each item of the list
listeach(l, function (x) {
console.log(x)
})
closing remarks
It appears as tho you can use an Object in lieu of an Array. The accepted answer (at this time) shows a very narrow understanding of how an object could be used to solve your problem. After this contrived demonstration, are you confident that you are using Objects properly and effectively?
Do you know how to implement an object? Could you fulfill this contract (below)? What I mean by that, is could you write the functions object, set, and get such that the following expressions evaluated to their expected result?
In case it's not obvious, you're not allowed to use Object to make it happen. The whole point of the exercise is to make a new data type that you don't already have access to
m = object() // m
set(m, key, x) // m
get(m, key) // x
set(m, key2, y) // m
get(m, key2) // y
set(m, key3, set(object(), key4, z)) // m
get(get(m, key3), key4) // z
I'll leave this as an exercise for you and I strongly encourage you to do it. I think you will learn a lot in the process and develop a deep understanding and appreciation for what higher-level data types like Array or Object give to you

Since this is a homework I feel like I shouldn't solve it for you, but rather help you in the right direction.
Like Slasher mentioned you can use objects
With JavaScript object one book would look something like
const book = {
title: 'my awesome title',
type: 'novel'
};
book is the object
title is a property with a value 'my awesome title'
type is a property with a value 'novel'
But objects can also have other objects as values. Something like
const BookShelf= {
Book1: {
Title: 'my awesome title',
Type: 'novel'
},
Book2: {
Title: 'my horrible title',
Type: 'sci-fi'
}
};
You can reference the books in the bookshelf in two ways
const book1 = BookShelf.Book1 // Returns the book1 object
const title1 = Book1.Title; // Get the title
const sametitle = BookShelf.Book1.Title // Returns title for book1, same as above.
You can also use brackets:
const book1 = BookShelf['Book1'];
const title1 = BookShelf['Book1']['Title];
You can even make new properties on a object like this:
const Book3 = {
Title: 'running out of ideas'
Type: 'memoir'
};
BookShelf['Book3'] = Book3;
Now the BookShelf has a Book3 property. So your BookShelf object looks like
const BookShelf= {
Book1: {
Title: 'my awesome title',
Type: 'novel'
},
Book2: {
Title: 'my horrible title',
Type: 'sci-fi'
},
Book3 = {
Title: 'running out of ideas'
Type: 'memoir'
};
};
That should get you started :)

JavaScript Objects is a good way to go
1- define a new object:
var myVar = {};
or
var myVar = new Object();
2- usage
// insert a new value, it doesn't matter if the value is a string or int or even another object
// set a new value
myVar.myFirstValue="this is my first value";
// get existing value and do what ever you want with it
var value = myVar.myFirstValue

resolving a javascript and database table logic situation

When I query a database table, I get back values "yes" or "no" for records that represent whether an item is present or not (the item is the column name). I want to create a string that represents the products that are available by name (rather than what I am doing now "kitchen table =" + kitchenTable;
I am thinking this can be solved (poorly) by a series of if statements setting variables to either the product name or to "" and then include all variables in the string
var kt;
if (kitchenTable == yes) kt = "kitchen table";
else kt = "";
if (kitchenCabinet == yes) kc = "kitchen cabinet";
else ka = "";
output = kt + ', ' + kc;
There are about 50 items that can be presented to the user, is there a more efficient way of accomplishing this task?? One option is to change how values are entered into the datbase table such that instead of yes, its the item name but this seems like a poorer way to resolve the issue

Of course you don't give all the details about how do you make query so that is an imaginary mockup of a function simulating query
var available = [];
var result = query("kitchen table");
result === "yes" && ( available.push("kitchen table") );
......
var output = available.join();

What you want is actually built into javascript itself.
I would say using an object literal will really simply your life in this situation by organizing your code and turning it into a more readable format.
I would also recommend turning your server data into true and false as this is a standardized way to communicated a Boolean and allows for the method below to work as it does:
// From server response
var results = {
kitchenCabinet: true,
kitchenTable: true
}
// Use this for your storage of all related items
var kitchenProps = {
kitchenCabinet: 'kitchen cabinet',
kitchenTable: 'kitchen table'
}
// Reuse this function for each time your need a new category (masterBathroomProps...)
function getItemDataIfExists(results, hashTable){
'use strict';
var output = 'Your total is: ';
for (var item in results) {
if (!results.hasOwnProperty(item)) return;
if (results[item]) output += 'A '+hashTable[item]+' ';
}
return output;
}
getItemDataIfExists(results, kitchenProps);
Explanation:
You loop through a result set of an object containing keys names and true false values. In the loop, if the keyname's value is true, then use that keyname to access the properties (in this case a string of your choice. The "key" here is that the key names in each object must line up.
Here is a live demo:
http://codepen.io/nicholasabrams/pen/JXXbYz?editors=0010

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.