For learning purposes I am creating a Todo app in JavaScript.
I have a function that takes the input value(Task) and push it to an array of objects.
I want to be able to remove the object task out of the array listOfTask when button delete is clicked and I want to switch the completed property of task to true when button completed is clicked. My problem is that the user can click randomly any object in the array. So I can not link the event click to the object that I want to manipulate using index. Any ideas on how to achieve this will be highly appreciated. By the way, this is my fisrt time posting a question so please let me know if my question needs improvment or clarification.
let listofTask=[];
function addTask(){
let taskAdded= document.getElementById('input1').value;
let task=new Object;
task.task=taskAdded;
task.completed=false;
listOfTask.push(task);
appendTask(listOfTask);
}
So the function appendTask() craetes two buttons per each task and print them into the HTML
function appendTask(array){
if(array.length>0){
let div=document.getElementById('show-tasks');
let ul= document.createElement('ul');
let completedButton= document.createElement('input');
completedButton.value= 'Completed';
completedButton.type='button';
completedButton.onclick=function completedTask(){
this.parentNode.classList.add("mark-completed");
}
let deleteButton= document.createElement('input');
deleteButton.value='Delete';
deleteButton.type='button';
deleteButton.onclick= function deleteTask(){
this.parentNode.remove();
}
ul.innerHTML=ul.innerHTML+`<li>${array[array.length-1].task}</li>
`;
ul.appendChild(completedButton);
ul.appendChild(deleteButton);
div.appendChild(ul)
}
}
At this point I am able to succesfully mark a task as completed and remove it from the HTML but I want to be able to manipulate the objects inside the array as well.
Thank you!
Always glad to see new developers diving right in!
One way of achieving your desired goal is to give each Object a property id which uniquely identifies it. Then, when clicking the delete-button, you can use the Array function findIndex to find the element to remove.
Okay guys so I've run into a problem on some code I've been working on. In the code below, I'm trying to console log the length of an array, but after printing to the console, I get an output of 0 for the array's length, and when I print the array itself, it shows that it is empty, but I can click the drop down arrow and see the element inside it.
// randomly selects card from array
export const selectCard = arr => {
const randomArr = Math.floor(Math.random() * arr.length);
console.log(arr.length);
console.log(arr);
}
Image of logged array length and empty array with an element inside.
To test what was happening, I decided to console log the array in a different function that is in the same file where the array is created. The array (blackCards) is stored in an object.
let packArr = {
data: {},
packToUse: [],
whiteCards: [],
blackCards: [],
};
Console logging the array (blackCards) in another function logs this:
const seperatePacks = (data) => {
// add white cards to array
packArr.whiteCards.push(data.whiteCards);
// add black cards to array
packArr.blackCards.push(data.blackCards);
// console log blackCards array
console.log(packArr.blackCards);
};
Image of logged array from a different function which is within the same file where the array is created and stored.
Here's a little more about how my code works. When a user clicks on a button, an event listener is activated, which calls other functions that eventually get json from a sever, then I add that data to the array, which you see in the code above. So now that you know how the code works, I can get to what is causing me to be even more confused. So, on the first click, I get the outcome of all the previous code and images combined, but if i click on the same button again, or click on a different one, I get the desired outcome (if I click on two button I get two elements in the array, so it's working correct). So, two or more clicks and the program works the way it should. Any help here would be great. Also sorry if this post was a little scuffed, it is my first one.
Here are the functions that eventually call selectCard
elements.packs.addEventListener("click", (e) => {
const packID = e.target.closest(".pack").id;
if (packID) {
packsToUse(packID);
// create black cards
blackCardDisplay(packArr.blackCards);
}
});
Above is the listener that was mentioned earlier, which calls the function below, that will call selectCard.
export const blackCardDisplay = data => {
const card = `
<div class="cards card--black">
<h1 class="card--black-text card--text">${selectCard(data)}</h1>
</div>
`;
}
Here is the output after pressing two buttons. The array should contain two elements but in this case it only shows one. However when I expand the array, it shows a length of two instead of just one.
Console image of two button clicks
EDIT: After reading some of the comments I realized I forgot to mention that the contents of blackCards is an array. So I have an array within an array.
So, after reading some comments I decided to implement #charlietfl's comment that maybe the array was console logged before the ajax call had been completed. Although this did not explicitly fix the problem, it set me on the right track to the solution.
Here is how I solved this problem:
I took the comments given about the console log completing before the ajax call could finish, and from there, I did some research and found this very simple article:
https://www.programmersought.com/article/26802083505/
In this article was an example using the setTimeout() method.
Here is the final solution to my problem.
export const selectCard = arr => {
const randomArr = Math.floor(Math.random() * arr.length);
setTimeout(() => {
console.log(arr.length);
console.log(arr)
}, 1000);
}
Here is the output after adding the setTimeout() method on the first button press.
Image of solved array length and array console log
I'm not aware if this is the best solution for the problem, because I've seen some people disapprove of using this method in the past, but it will work fine for what I'm doing at this point. If anyone has a better way of solving this I would love to hear it!
I'm currently trying to find a way to match user input to find a user in Discord, for commands that we didn't necessarily want tagging the user. As it is, the method I'm using to get that username is
var member = message.guild.members.find('nickname', `${searched}`);
However this only pulls the name if it's an exact match, which is kind of annoying.
How would I go about pulling a name with only a partial bit of it?
For further clarification, the variable 'searched' is what I'm looking to replace in order to match the string provided by user input to the nickname attribute in Discord's members objects.
EDIT
Found what I was looking for
var member = message.guild.members.find(element => element.nickname.includes(searched) == true);
This should work if members is an array. It should match nickname anywhere in the string.
const nickRegx = new RegExp('nickname')
var member = message.guild.members.find((member => nickRegx.test(member));
Found the answer to my own question after an hour or so
var member = message.guild.members.find(element => element.nickname.includes(searched) == true);
still learning some javascript here, got done other things but now the final and most important part of it.
I have two html pages - one of which uses javascript to dynamically add text-fields (and to remove them of course) (genmain.html) and the other one where the text field input should go(table.html).
So i have already created a function to retrieve the array of values.
function getElementArray(divName){
var names = document.getElementsByName("namefield");
}
The variable names is an array and it has all the values from fields.
The problem is I would like to set these values from array to the values of another div on the page. After some searching i understood that it could be done with 'id'-s but i'm not that sure and don't completely understand how.
Let's say i have a lot of div's on another page (table.html) but some of them have id="MAIN". I would like to change the value inside of the div
For example
<div id="MAIN">THIS PART I WANT TO CHANGE</div>
Javascript is not part of my school system and i've done CodeAcademy tutorials and that's the most i've got about this, I hope you guys can help with my issue.
The variable names is an array and it has all the values from fields.
function getElementArray(divName){
var names = document.getElementsByName("namefield");
}
Nope, you've only got reference to the elements here. You've not got the value yet.
You can get the values by iterating through the names Nodelist array and use names[i].value
The problem is I would like to set these values from array to the
values of another div on the page
If it's going to be in same page, then use innerHTML or textContent property of the DOM to assign the value.
document.getElementById("MAIN").textContent= names[1].value;
Just for demo purpose am using names[1] here so it will load the second input value.
Let's say i have a lot of div's on another page (table.html) but some
of them have id="MAIN". I would like to change the value inside of the
div
Once you move to another page, the javascript state will be lost. So you wont have access to names inside that page.
Either you must store the values into localStorage and retrieve in next page.
Else add the values to query string of your URL and retrive it there.
Edit: Update based on comments
Let us assume you have var names = document.getElementsByName("namefield"); so to store the values inside localStorage.
var myValues = [],
names = document.getElementsByName("namefield");
for(var i = 0; i < names.length; i++) {
myValues.push(names[i].value);
}
localStorage.myValues = JSON.stringify(myValues);
Now if your next page, Iinside window.onload event:
window.onload = function() {
var myValues = localStorage.getItem("myValues") ? JSON.parse(localStorage.getItem("myValues")) : [],
divElements = document.querySelectorAll("#MAIN");
for(var i =0; i < myValues.length; i++) {
divElements[i].textContent = myValues[i];
}
}
If you want to set or change the contents of an element, you can use the innerHTML property.
So in your case, document.getElementById("MAIN").innerHTML = "Whatever you want";
For the record, names in your example technically isn't an array, but a NodeList. See https://developer.mozilla.org/en/docs/Web/API/NodeList#Why_is_NodeList_not_an_Array.3F.
I'm trying to test out Firebase to allow users to post comments using push. I want to display the data I retrieve with the following;
fbl.child('sell').limit(20).on("value", function(fbdata) {
// handle data display here
}
The problem is the data is returned in order of oldest to newest - I want it in reversed order. Can Firebase do this?
Since this answer was written, Firebase has added a feature that allows ordering by any child or by value. So there are now four ways to order data: by key, by value, by priority, or by the value of any named child. See this blog post that introduces the new ordering capabilities.
The basic approaches remain the same though:
1. Add a child property with the inverted timestamp and then order on that.
2. Read the children in ascending order and then invert them on the client.
Firebase supports retrieving child nodes of a collection in two ways:
by name
by priority
What you're getting now is by name, which happens to be chronological. That's no coincidence btw: when you push an item into a collection, the name is generated to ensure the children are ordered in this way. To quote the Firebase documentation for push:
The unique name generated by push() is prefixed with a client-generated timestamp so that the resulting list will be chronologically-sorted.
The Firebase guide on ordered data has this to say on the topic:
How Data is Ordered
By default, children at a Firebase node are sorted lexicographically by name. Using push() can generate child names that naturally sort chronologically, but many applications require their data to be sorted in other ways. Firebase lets developers specify the ordering of items in a list by specifying a custom priority for each item.
The simplest way to get the behavior you want is to also specify an always-decreasing priority when you add the item:
var ref = new Firebase('https://your.firebaseio.com/sell');
var item = ref.push();
item.setWithPriority(yourObject, 0 - Date.now());
Update
You'll also have to retrieve the children differently:
fbl.child('sell').startAt().limitToLast(20).on('child_added', function(fbdata) {
console.log(fbdata.exportVal());
})
In my test using on('child_added' ensures that the last few children added are returned in reverse chronological order. Using on('value' on the other hand, returns them in the order of their name.
Be sure to read the section "Reading ordered data", which explains the usage of the child_* events to retrieve (ordered) children.
A bin to demonstrate this: http://jsbin.com/nonawe/3/watch?js,console
Since firebase 2.0.x you can use limitLast() to achieve that:
fbl.child('sell').orderByValue().limitLast(20).on("value", function(fbdataSnapshot) {
// fbdataSnapshot is returned in the ascending order
// you will still need to order these 20 items in
// in a descending order
}
Here's a link to the announcement: More querying capabilities in Firebase
To augment Frank's answer, it's also possible to grab the most recent records--even if you haven't bothered to order them using priorities--by simply using endAt().limit(x) like this demo:
var fb = new Firebase(URL);
// listen for all changes and update
fb.endAt().limit(100).on('value', update);
// print the output of our array
function update(snap) {
var list = [];
snap.forEach(function(ss) {
var data = ss.val();
data['.priority'] = ss.getPriority();
data['.name'] = ss.name();
list.unshift(data);
});
// print/process the results...
}
Note that this is quite performant even up to perhaps a thousand records (assuming the payloads are small). For more robust usages, Frank's answer is authoritative and much more scalable.
This brute force can also be optimized to work with bigger data or more records by doing things like monitoring child_added/child_removed/child_moved events in lieu of value, and using a debounce to apply DOM updates in bulk instead of individually.
DOM updates, naturally, are a stinker regardless of the approach, once you get into the hundreds of elements, so the debounce approach (or a React.js solution, which is essentially an uber debounce) is a great tool to have.
There is really no way but seems we have the recyclerview we can have this
query=mCommentsReference.orderByChild("date_added");
query.keepSynced(true);
// Initialize Views
mRecyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
mManager = new LinearLayoutManager(getContext());
// mManager.setReverseLayout(false);
mManager.setReverseLayout(true);
mManager.setStackFromEnd(true);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(mManager);
I have a date variable (long) and wanted to keep the newest items on top of the list. So what I did was:
Add a new long field 'dateInverse'
Add a new method called 'getDateInverse', which just returns: Long.MAX_VALUE - date;
Create my query with: .orderByChild("dateInverse")
Presto! :p
You are searching limitTolast(Int x) .This will give you the last "x" higher elements of your database (they are in ascending order) but they are the "x" higher elements
if you got in your database {10,300,150,240,2,24,220}
this method:
myFirebaseRef.orderByChild("highScore").limitToLast(4)
will retrive you : {150,220,240,300}
In Android there is a way to actually reverse the data in an Arraylist of objects through the Adapter. In my case I could not use the LayoutManager to reverse the results in descending order since I was using a horizontal Recyclerview to display the data. Setting the following parameters to the recyclerview messed up my UI experience:
llManager.setReverseLayout(true);
llManager.setStackFromEnd(true);
The only working way I found around this was through the BindViewHolder method of the RecyclerView adapter:
#Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
final SuperPost superPost = superList.get(getItemCount() - position - 1);
}
Hope this answer will help all the devs out there who are struggling with this issue in Firebase.
Firebase: How to display a thread of items in reverse order with a limit for each request and an indicator for a "load more" button.
This will get the last 10 items of the list
FBRef.child("childName")
.limitToLast(loadMoreLimit) // loadMoreLimit = 10 for example
This will get the last 10 items. Grab the id of the last record in the list and save for the load more functionality. Next, convert the collection of objects into and an array and do a list.reverse().
LOAD MORE Functionality: The next call will do two things, it will get the next sequence of list items based on the reference id from the first request and give you an indicator if you need to display the "load more" button.
this.FBRef
.child("childName")
.endAt(null, lastThreadId) // Get this from the previous step
.limitToLast(loadMoreLimit+2)
You will need to strip the first and last item of this object collection. The first item is the reference to get this list. The last item is an indicator for the show more button.
I have a bunch of other logic that will keep everything clean. You will need to add this code only for the load more functionality.
list = snapObjectAsArray; // The list is an array from snapObject
lastItemId = key; // get the first key of the list
if (list.length < loadMoreLimit+1) {
lastItemId = false;
}
if (list.length > loadMoreLimit+1) {
list.pop();
}
if (list.length > loadMoreLimit) {
list.shift();
}
// Return the list.reverse() and lastItemId
// If lastItemId is an ID, it will be used for the next reference and a flag to show the "load more" button.
}
I'm using ReactFire for easy Firebase integration.
Basically, it helps me storing the datas into the component state, as an array. Then, all I have to use is the reverse() function (read more)
Here is how I achieve this :
import React, { Component, PropTypes } from 'react';
import ReactMixin from 'react-mixin';
import ReactFireMixin from 'reactfire';
import Firebase from '../../../utils/firebaseUtils'; // Firebase.initializeApp(config);
#ReactMixin.decorate(ReactFireMixin)
export default class Add extends Component {
constructor(args) {
super(args);
this.state = {
articles: []
};
}
componentWillMount() {
let ref = Firebase.database().ref('articles').orderByChild('insertDate').limitToLast(10);
this.bindAsArray(ref, 'articles'); // bind retrieved data to this.state.articles
}
render() {
return (
<div>
{
this.state.articles.reverse().map(function(article) {
return <div>{article.title}</div>
})
}
</div>
);
}
}
There is a better way. You should order by negative server timestamp. How to get negative server timestamp even offline? There is an hidden field which helps. Related snippet from documentation:
var offsetRef = new Firebase("https://<YOUR-FIREBASE-APP>.firebaseio.com/.info/serverTimeOffset");
offsetRef.on("value", function(snap) {
var offset = snap.val();
var estimatedServerTimeMs = new Date().getTime() + offset;
});
To add to Dave Vávra's answer, I use a negative timestamp as my sort_key like so
Setting
const timestamp = new Date().getTime();
const data = {
name: 'John Doe',
city: 'New York',
sort_key: timestamp * -1 // Gets the negative value of the timestamp
}
Getting
const ref = firebase.database().ref('business-images').child(id);
const query = ref.orderByChild('sort_key');
return $firebaseArray(query); // AngularFire function
This fetches all objects from newest to oldest. You can also $indexOn the sortKey to make it run even faster
I had this problem too, I found a very simple solution to this that doesn't involved manipulating the data in anyway. If you are rending the result to the DOM, in a list of some sort. You can use flexbox and setup a class to reverse the elements in their container.
.reverse {
display: flex;
flex-direction: column-reverse;
}
myarray.reverse(); or this.myitems = items.map(item => item).reverse();
I did this by prepend.
query.orderByChild('sell').limitToLast(4).on("value", function(snapshot){
snapshot.forEach(function (childSnapshot) {
// PREPEND
});
});
Someone has pointed out that there are 2 ways to do this:
Manipulate the data client-side
Make a query that will order the data
The easiest way that I have found to do this is to use option 1, but through a LinkedList. I just append each of the objects to the front of the stack. It is flexible enough to still allow the list to be used in a ListView or RecyclerView. This way even though they come in order oldest to newest, you can still view, or retrieve, newest to oldest.
You can add a column named orderColumn where you save time as
Long refrenceTime = "large future time";
Long currentTime = "currentTime";
Long order = refrenceTime - currentTime;
now save Long order in column named orderColumn and when you retrieve data
as orderBy(orderColumn) you will get what you need.
just use reverse() on the array , suppose if you are storing the values to an array items[] then do a this.items.reverse()
ref.subscribe(snapshots => {
this.loading.dismiss();
this.items = [];
snapshots.forEach(snapshot => {
this.items.push(snapshot);
});
**this.items.reverse();**
},
For me it was limitToLast that worked. I also found out that limitLast is NOT a function:)
const query = messagesRef.orderBy('createdAt', 'asc').limitToLast(25);
The above is what worked for me.
PRINT in reverse order
Let's think outside the box... If your information will be printed directly into user's screen (without any content that needs to be modified in a consecutive order, like a sum or something), simply print from bottom to top.
So, instead of inserting each new block of content to the end of the print space (A += B), add that block to the beginning (A = B+A).
If you'll include the elements as a consecutive ordered list, the DOM can put the numbers for you if you insert each element as a List Item (<li>) inside an Ordered Lists (<ol>).
This way you save space from your database, avoiding unnecesary reversed data.