Develop Reference

move up and down array values on click options using knockout js?

I am new in knockoutjs, I saw an example, which moves up and down array values by selecting the dropdown values of the index in the option. But its problem is they dont't move the values correctly. And after changing the array position options in select box will be changed..
var viewModel = function() {
var self = this;
var Item = function(name, pos) {
this.name = ko.observable(name);
this.position = ko.observable(pos);
var oldPosition = pos;
this.position.subscribe(function(newValue) {
self.reposition(this, oldPosition, newValue);
oldPosition = newValue;
}, this);
};
this.items = [
new Item("item Three", "3"),
new Item("item One", "1"),
new Item("item Two", "2"),
new Item("item Five", "5"),
new Item("item Four", "4"),
new Item("item Six", "6")
];
self.orderedItems = ko.computed(function() {
return ko.utils.arrayFilter(this.items, function(item) {
return true;
}).sort(function(a, b) {
return a.position() - b.position();
});
});
self.curName = ko.observable();
self.reposition = function(item, oldPosition, newPosition) {
console.debug("Reposition", item, oldPosition, newPosition);
};
};
ko.applyBindings(viewModel);
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<div class='liveExample'>
<ul data-bind="foreach: orderedItems">
<li>
<div> <span data-bind="text: name"> </span> has Position:
<select id="pos" data-bind=" options: orderedItems,
optionsText: 'position',
optionsValue: 'position',
value: position "></select>
</div>
</li>
</ul>
</div>
this is my sample code, i want to show array index position should be show in the dropdown. I want to select the index value in the dropdown the position of the array values should be change but not the opitions. How is it possible with knockout js.

So this one is a little more tricky than normal since you are basing your index on a property of the Item. It's not wrong, it just adds more complexity.
First you have to create the array of "indexes" since you aren't actually changing the index of the items, they are just computed off of the position property.
this.items() has been changed to an observableArray to propagate/bubble changes of the items to other functions. Now you could include an "Add Item" feature, add it to the the items array and everything would updated correctly.
I removed the subscribe function in the Item constructor, it was causing too many issues firing off when it didn't need to. Instead I attached an event handler to the select box that can manage the items and removed the two way binding of the value by getting the value().
Hope this helps and good luck!
var viewModel = function() {
var self = this;
// UPDATED: Removed the subscribe function
var Item = function(name, pos) {
this.name = ko.observable(name);
this.position = ko.observable(pos);
};
// UPDATED: Changed to observable so you can change items here and it will propogate down to the computed functions
this.items = ko.observable([
new Item("item Three", "3"),
new Item("item One", "1"),
new Item("item Two", "2"),
new Item("item Five", "5"),
new Item("item Four", "4"),
new Item("item Six", "6")
]);
// ADDED: Create array of index options based on length
this.positions = ko.computed(function(){
var numArray = [];
for(i = 0; i < self.items().length; i++) {
numArray.push(i + 1)
}
return numArray;
})
self.orderedItems = ko.computed(function() {
return ko.utils.arrayFilter(self.items(), function(item) {
return true;
}).sort(function(a, b) {
return a.position() - b.position();
});
});
self.curName = ko.observable();
/**
* UPDATED: Get item at selected position, change it to the current
* items position, then update current items position to the selected position;
*/
self.reposition = function(item, event) {
var selectedPosition = event.target.value;
var itemAtPosition = ko.utils.arrayFirst(self.items(), function(i){
return i.position() === selectedPosition;
})
itemAtPosition.position(item.position());
item.position(event.target.value)
};
};
ko.applyBindings(viewModel);
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<div class='liveExample'>
<ul data-bind="foreach: orderedItems">
<li>
<div> <span data-bind="text: name"> </span> has Position:
<select id="pos" data-bind=" options: positions(),
value: position(), event: { change: reposition} "></select>
</div>
</li>
</ul>
</div>

Create grid with knockoutjs

Let's say we have an observable array of N+1 elements. What i would like to achive is to build 3 by X grid with buttons from these elements. Like phone keypad or something like this.
What i have done so far is created a table with foreach and if in it:
<table>
<tbody data-bind="foreach: tableList">
<!-- ko if: isEof($index()) -->
<tr>
<!-- /ko -->
<td><button data-bind="text: name"></button></td>
<!-- ko if: isEof($index()) -->
</tr>
<!-- /ko -->
</tbody>
</table>
isEof() function should determine by list index wether we have already 3 elements rendered. If yes, then it will render tags. Also if index is 0, then it also renders elements.
This is the code of the function:
function TableItem(data){
this.id=ko.observable(data.id);
this.name=ko.observable(data.name);
this.isEof = function(index){
if(index ==0){
return true;
}else{
if((index+3) % 3 === 0){
return true;
}else{
return false;
}
}
}
}
But i'm facing two problems with this setup.
1) With these if blocks enabled, button name binding does not work. When i remove ko if blocks, it will be rendered correctly.
2) ko if statements does not seem to work correctly. It will render out only those lines, where is also allowed to render.
I've made JSFiddle sample of my solution: http://jsfiddle.net/kpihus/3Lw7xjae/2/

I would create a ko.computed that converts your list of table items into an array of arrays:
var TableItem = function TableItem(data) {
this.id = ko.observable(data.id);
this.name = ko.observable(data.name);
};
var Vm = function Vm() {
this.tableItems = ko.observableArray([]);
this.columnCount = ko.observable(3);
this.columns = ko.computed(function() {
var columns = [],
itemCount = this.tableItems().length,
begin = 0;
// we use begin + 1 to compare to length, because slice
// uses zero-based index parameters
while (begin + 1 < itemCount) {
columns.push( this.tableItems.slice(begin, begin + this.columnCount()) );
begin += this.columnCount();
}
return columns;
// don't forget to set `this` inside the computed to our Vm
}, this);
};
vm = new Vm();
ko.applyBindings(vm);
for (var i = 1; i < 15; i++) {
vm.tableItems.push(new TableItem({
id: i,
name: "name: " + i
}));
}
This way, you can display your table by nesting two foreach bindings:
<table>
<tbody data-bind="foreach: { data: columns, as: 'column' }">
<tr data-bind="foreach: column">
<td>
<button data-bind="text: name">A</button>
</td>
</tr>
</tbody>
</table>
JSFiddle
If you haven't worked with ko.computed before, they track whatever observables are accessed inside of them — in this case, this.tableItems and this.columnCount —, and whenever one of them changes, they run again and produce a new result.
this.columns takes our array of table items
[TableItem, TableItem, TableItem, TableItem, TableItem, TableItem]
and groups them by this.columnCount into
[[TableItem, TableItem, TableItem], [TableItem, TableItem, TableItem]]

We can achieve this by simply passing $root which will have tableList and do the looping in simple way .
View Model:
function TableItem(data) {
var self = this;
self.id = ko.observable(data.id);
self.name = ko.observable(data.name);
self.pickarray = ko.observableArray();
self.isEof = function (index, root) {
if (index === 0) {
self.pickarray(root.tableList().slice(index, index + 3));
return true;
} else if ((index + 3) % 3 === 0) {
self.pickarray(root.tableList().slice(index, index + 3));
return true;
} else {
return false;
}
}
}
var vm = function () {
this.tableList = ko.observableArray();
for (var i = 1; i < 15; i++) {
this.tableList.push(new TableItem({
id: i,
name: "name: " + i
}));
}
}
ko.applyBindings(new vm());
View :
<table data-bind="foreach:tableList">
<tr data-bind="if:isEof($index(),$root)">
<!-- ko foreach: pickarray -->
<td>
<button data-bind="text: id"></button>
</td>
<!-- /ko -->
</tr>
</table>
Trick here is very simple we just need to conditionally fill pickarray which does the job for us .
Working Fiddle here

Knockout: remove select options from array when already in use

I have a little knockout form which I am able to duplicate using a button to allow multiple sets of data to be provided.
However, each value for the 'sample rate' select can only be used once. For example, the first form by default is set to 192000. So when I click 'add srate element' the form that is generated should not include 192000 as an option in the Sample rate drop-down.
Obviously if the Sample rate for the first form is set to something else, that value should be removed for the second form, and so on.
How do I remove the already-selected Sample rate from the array when a new form is added, so that it is not available in further copies of the form? It is even possible, given the structure of the view model?
There's a fiddle here: http://jsfiddle.net/3lliot/x3cg131g/
There's a bit of logic included already to prevent more than 6 forms.
Any tips will be appreciated ...
Html code:
<body>
<ul data-bind="foreach: forms">
<li>
<!-- This is a *view* - HTML markup that defines the appearance of your UI -->
<p><span style="color:#AB0002">Sample rate element <span data-bind="text: formNum"></span></span>
</p>
<p>Sample rate (Hz):
<select data-bind="options: $parent.sampleRate, value: selectedSampleRate"></select>
</p>
<p>TDM channels per line:
<select data-bind="options: tdmChans, value: selectedTdmchan"></select>
</p>
</li>
</ul>
<button data-bind="click: addForm">Add <srate> element</button>
<button data-bind="click: removeForm">Remove</button>
<hr/>
<ul data-bind="foreach: forms">
<li>
<!-- render the json -->
<p class="code"><srate id="<span data-bind="text: formNum"></span>">
<br/> <sample_rate><span data-bind="text: selectedSampleRate"></span></sample_rate>
<br/> <tdm_chan><span data-bind="text: selectedTdmchan"></span></tdm_chan>
<br/>
</p>
</li>
</ul>
</body>
JS code:
window.onload = startKnockout;
var formNum;
var i = -1;
function Form() {
var self = this;
// Declare observables
self.selectedSampleRate = ko.observable();
self.selectedTdmchan = ko.observable();
self.formNum = ko.observable();
// Define controls
self.tdmChans = ko.computed(function() {
if (self.selectedSampleRate() == 44100 || self.selectedSampleRate() == 48000) {
return ['2', '4', '8', '16'];
} else if (self.selectedSampleRate() == 88200 || self.selectedSampleRate() == 96000) {
return ['2', '4', '8'];
} else if (self.selectedSampleRate() == 176400 || self.selectedSampleRate() == 192000) {
return ['2', '4'];
} else {
// do nothing
}
}, self);
i++;
self.formNum = i;
}
var Vm = function() {
var self = this;
var item = 0;
self.forms = ko.observableArray([]);
self.forms.push(new Form());
item++;
self.addForm = function() {
if (i < 5) {
self.forms.push(new Form());
item++;
} else {
alert("Can't have more than 6 <srate> elements!")
}
};
self.removeForm = function() {
if (item > 1) {
self.forms.splice(item - 1, 1);
item--;
i--;
} else {
alert("Must have at least one <srate> element!")
}
};
self.sampleRate = ko.observableArray(['192000', '176400', '96000', '88200', '48000', '44100']);
return self;
}
// Activates knockout.js
function startKnockout() {
ko.applyBindings(new Vm());
};

Take a look at this:
http://jsfiddle.net/martinbooth/x3cg131g/1/
importantly, compute the available samples rates based on what has been selected in other forms:
self.sampleRates = ko.computed(function(){
var formsValue = forms(),
availableSampleRates = ko.utils.arrayFilter(allSampleRates, function(sampleRate){
return !ko.utils.arrayFirst(formsValue, function(form){
return form != self && form.selectedSampleRate() === sampleRate;
});
});
return availableSampleRates;
});

removing a parent in a knockout function from nested loop

In my view I am looping through an observableArray (itemGroup) that has one property that is also an observableArray (item). I have a method to remove an entire itemGroup and one to remove an item from and itemGroup but I would like to add in some logic along the lines of it there is only 1 item left in the group removing that item should also remove the itemGroup.
here is an example of the relevant parts of my view model and view.
my JS
var ItemModel = function(item) {
var self = this;
self.name = ko.observable(item.name);
self.price = ko.observable(item.price);
};
var ItemGroupModel = function(itemGroup) {
var self = this;
self.order = ko.observable(itemGroup.order);
self.items = ko.observableArray(ko.utils.arrayMap(itemGroup.items, function(item){
return new ItemModel(item);
}));
self.type = ko.observable(item.type);
self.removeItem = function(item) {
self.items.remove(item);
}
};
var ViewModel = function(data) {
var self = this;
self.itemGroups = ko.observableArray(ko.utils.arrayMap(data.itemGroups, function(itemGroup) {
return new ItemGroupModel(item);
}));
// some other properties and methods
self.removeItemGroup = function(itemGroup) {
self.itemGroups.remove(itemGroup);
}
};
My View
<ul data-bind="foreach: {data: VM.itemGroups, as: 'itemGroup'}">
<li>
<button data-bind="click: $root.VM.removeItemGroup">X</button>
<ul data-bind="foreach: {data: itemGroup.items, as: 'item'}">
<li>
<!-- ko if: itemGroup.items().length > 1 -->
<button data-bind="click: itemGroup.removeItem">X</button>
<!-- /ko -->
<!-- ko ifnot: itemGroup.items().length > 1 -->
<button data-bind="click: function () { $root.VM.removeItemGroup($parent) }">X</button>
<!-- /ko -->
</li>
</ul>
</li>
</ul>
This works but to me it isnt ideal. It is my understanding that knockout should help me get away from using an anonymous function like "function () { $root.VM.removeItemGroup($parent) }" but I am not sure how to do it another way. Also removing the if and ifnot statements would be good to clean up as well.

I would like to give my solution
send index of itemGroups and items as argument to remove method.
Hope you know how to send index
Then check the length of itemGroups
self.remove(itemGroupsIndex,itemsIndex) {
var itemGroupsLength = self.itemGroups()[itemGroupsIndex].items().length;
if(itemGroupsLength = 1) {
self.itemGroups.remove(itemGroupsIndex);
}
else {
self.itemGroups()[itemGroupsIndex].items.remove(itemsIndex);
}
};

knockout binding after array updated

I have an array that I'm removing items from but I'm keeping count of the number of items to do UI formatting. I need to be able to have the bind update.
ko.applyBindings(viewModel);
getFoos();
var viewModel = {
foos: ko.observableArray([]),
reloadFoos: function () {
getFoos();
},
removeFoo: function () {
remove(this);
}
};
var foo = function () {
this.Id = ko.observable();
this.Name = ko.observable();
this.Count = ko.observable();
};
function remove(foo) {
viewModel.foos.splice(viewModel.foos.indexOf(foo), 1);
viewModel.foos.each(function(index) {
viewModel.foos[index].Count = index%10 == 0;
});
}
function getFoos() {
viewModel.foos([]);
$.get("/myroute/", "", function (data) {
for (var i = 0; i < data.length; i++) {
var f = new foo();
f.Id = data[i];
f.Name = data[i];
f.Count = i%10 == 0;
viewModel.foos.push(f);
}
});
}
<div data-bind="foreach: foos">
<div style="float: left">
<a href="javascript:void(0);" data-bind="click : $parent.removeFoo, attr: { id: Id }">
<label data-bind="value: Name"></label>
</a>
</div>
<!-- ko if: Count -->
<div style="clear: left"></div>
<!-- /ko -->
</div>
When the click event fires the item is removed from the array but the if bind doesn't get updated and the ui formatting is off. I'm trying to keep from reloading the data because the ui block bounces as it removes and reloads.

Your UI is not being updated because when you do your assignment to Count, you aren't assigning as an observable. You are replacing the observable with a straight boolean value. So, your assignment calls like this one:
viewModel.foos[index].Count = index%10 == 0;
Will cause viewModel.foos[index].Count to be equal to true or false and the value won't be stored in the observable.
That line should be this instead:
viewModel.foos[index].Count(index%10 == 0);
That will set the observable correctly. Note that you must change all of your assignments to observables to be set this way. See the "Reading and Writing Observables" section of this page: Knockout Observables.