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
Website that I'm making is in two different languages each data is saved in mongodb with prefix _nl or _en
With a url I need to be able to set up language like that:
http://localhost/en/This-Is-English-Head/This-Is-English-Sub
My code look like that:
var headPage = req.params.headPage;
var subPage = req.params.subPage;
var slug = 'name';
var slugSub = 'subPages.slug_en';
var myObject = {};
myObject[slugSub] = subPage;
myObject[slug] = headPage;
console.log(myObject);
Site.find(myObject,
function (err, pages) {
var Pages = {};
pages.forEach(function (page) {
Pages[page._id] = page;
});
console.log(Pages);
});
After console.log it I get following:
{ 'subPages.slug_en': 'This-Is-English-Sub',
name: 'This-Is-English-Head' }
Is you can see objectname subPages.slug_en is seen as a String insteed of object name..
I know that javascript does not support underscores(I guess?) but I'm still looking for a fix, otherwise i'll be forced to change all underscores in my db to different character...
Edit:
The final result of console.log need to be:
{ subPages.slug_en: 'This-Is-English-Sub',
name: 'This-Is-English-Head' }
Insteed of :
{ 'subPages.slug_en': 'This-Is-English-Sub',
name: 'This-Is-English-Head' }
Otherwise it does not work
The reason you are seeing 'subPages.slug_en' (with string quotes) is because of the . in the object key, not the underscore.
Underscores are definitely supported in object keys without quoting.
Using subPages.slug_en (without string quotes) would require you to have an object as follows:
{ subPages: {slug_en: 'This-Is-English-Sub'},
name: 'This-Is-English-Head' }
Which you could set with the following:
myObject['subPages']['slug_en'] = subPage;
Or simply:
myObject.subPages.slug_en = subPage;
I've been trying to 'correlate' between user picked answers and an object property name so that if the two matches then it will display what is inside.
My program is a recipe finder that gives back a recipe that consists of the ingredients the user picked.
my code currently looks like:
//property are the ingredients and the value are the recipes that contain those ingredients. The map is automatically generated
``var map = {
"pork" : [recipe1, recipe2, ...],
"beef" : [],
"chicken" :[],
}
//this gets the user pick from the dom
var cucumber = specificVegetable[7];
var lemon = specificFruits[0];
//Then this code finds the intersection of the recipe(recipes that use more than one ingredients)
function intersect(array1, array2)
{
return array1.filter(function(n) {
return array2.indexOf(n) != -1
});
}
var recipiesWithLemon = map["lemon"]; **// makes the lemon object is map**
var recipiesWithCucumber = map["cucumber"]; **// makes the cucumber object in map**
//Here is where I am stuck
function check(){
var both = intersect(recipiesWithLemon, recipiesWithCucumber);
if ( cucumber.checked && lemon.checked){
for (var stuff in map){
if(stuff="cucumber" && stuff="lemon"){
return both;
}
}
}
}
check();
so basically what I tried to do was I made my intersect and then if user pick is lemon and cucumber then look at the properties in the map object. if the name of the property equals to the exact string then return both. That was the plan but the code does not work and I'm not sure how to fix it.
My plan is to write code for every possible outcome the user may makes so I need to find the correlation between the user pick and the map which stores the recipe. I realize this is not the most effective way but I'm stumped on how to do it another way.
Thanks for the help.
Im using the open source project jinqJs to simplify the process.
I also changed your map to an array of JSON objects. If you must have the map object not as an array, let me know. I will change the sample code.
var map = [
{"pork" : ['recipe1', 'recipe2']},
{"beef" : ['recipe3', 'recipe4']},
{"peach" :['recipe5', 'recipe6']},
{"carrot" :['recipe7', 'recipe8']}
];
var selectedFruit = 'peach';
var selectedVeggie = 'carrot';
var selections = [selectedFruit, selectedVeggie];
var result = jinqJs().from(map).where(function(row){
for(var f in row) {
if (selections.indexOf(f) > -1)
return true;
}
return false;
}).select();
document.body.innerHTML += '<pre>' + JSON.stringify(result, null, 2) + '</pre><br><br>';
<script src="https://rawgit.com/fordth/jinqJs/master/jinqjs.js"></script>
I have a variable being set as the .html(); of a <div />
The variable is the name of another variable. I want it to display the contents of the other variable, however it simply displays the name of the other variable.
How can I force it to show the variable contents rather than just a literal text string?
var clothing = 'dogeshop cryptoshop doge_clothing fyrstikken the_molly_machine peace_and_love moolah_market shibe_swag undieguys urban_graff kravshop got_doge mean_elephant the_dogedoor_store';
setInterval( function() {
var term = $("input").val();
$("#results").html(term);
}, 100);
When the user types 'clothing' into $("input"); the contents of the 'clothing' variable should be displayed in the $("#results"); <div />. Instead it just says 'clothing'.
Another way is to use object properties, like this
var obj = {};
obj.clothing = 'dogeshop cryptoshop doge_clothing fyrstikken the_molly_machine peace_and_love moolah_market shibe_swag undieguys urban_graff kravshop got_doge mean_elephant the_dogedoor_store';
setInterval( function() {
var term = $("input").val();
$("#results").html(obj[term]);
}, 100);
Here's the fiddle: http://jsfiddle.net/ZL7EQ/
The only way I know how to solve this is using eval:
$("#results").html(eval(term))
But you really shouldn't want to do that. :)
Use a dictionary.
// store strings in an object so you can look them up by key
var dict = {
clothing: 'dogeshop ...',
anotherKey: '...'
};
// update the result when the input changes
$('input').on('change', function() {
var result = dict[this.value]; // make sure the key exists
if (result) {
$('#results').val(result); // update the results
}
});
I use to make this mistake myself when working with jQuery.
Try instead:
$("#results").text(term);
Not sure what you have the interval for. You could just change the #results with a change event.
I need to use a variable when selecting data from a json source like this.
The json is retrieved with jquery getJSON().
"prices":[{
"fanta":10,
"sprite":20,
}]
var beverage = fanta;
var beverage_price = data.prices.beverage;
Now beverage_price = 10
var beverage = sprite;
var beverage_price = data.prices.beverage;
Now beverage_price = 20
When I try to do it like in the examples, the script tries to look up the beverage entry in prices.
Thanks a lot!!
You can access it like:
var beverage = 'fanta';
var beverage_price = data.prices[0][beverage];
As VisioN mentioned in the comment, data.prices is an array, you need to access its first element with [0] which contains prices { "fanta":10, "sprite":20}
here is the working example : http://jsfiddle.net/2E8AH/
Or else you can make data.prices an object like below : (if it is in your control)
var data = {
"prices" :
{
"fanta":10,
"sprite":20,
}
};
and can access without [0] like this : http://jsfiddle.net/Y8KtT/1/