Develop Reference

Javascript search for dropdown inside knockout data-bind foreach

Using knockout js
I have setup my dropdown inside a table as:
<tbody data-bind="foreach: items">
<tr>
<td id="tdName"><select class="form-control" data-bind="options: $parent.ddl, optionsText: 'firstName', value: selectedValue, optionsCaption: '--Select--', attr: { name: 'Items[' + $index() + '].Name', id: 'Items[' + $index() + '].Name'}"> </select></td>
</tr>
So it creates multiple rows of dropdowns. The above in html looks as below:
<select class="form-control" data-bind="options: $parent.ddl, optionsText: 'firstName', value: selectedValue, optionsCaption: '--Select--', attr: { name: 'Items[' + $index() + '].Name', id: 'Items[' + $index() + '].Name'}" name="Items[0].Name" id="Items[0].Name"><option value="">--Select--</option><option value="">Alex</option><option value="">Sam</option> </select>
I have a save button where I want to validate if this dropdown was selected on or not.
So I am trying to use the below code on save button click:
var selectList = $('#tdName > select');
for (var ddl of selectList ) {
if (ddl.value == '') {
ddl.className = "required text-danger form-control ddl-error"; }
}
In my console when I debug I can see the selectList as: select#Items[0].Name.form-control
So basically what I am trying to do above is loop through all the ddl and if no selection is made add the error class to it so that it is highlighted.
The issue is ddl.value is always '' so the dropdown is always highlighted.
Not sure here if I am looping though correctly here
I have my jsfiddle here as:
https://jsfiddle.net/aman1981/7wqvr854/51/
To see in action click add row, get data to populate the dropdown.
Would appreciate inputs.

You shouldn't access the DOM to check for selected values. You're already binding them to your viewmodel!
The validity check inside the Save method can access items directly:
self.save = function() {
var rows = self.items();
if (!rows.length)
alert("You cannot save an empty table");
else if (!rows.every(r => r.selectedSeperator())
alert("Some rows do not have a selected seperator");
// etc.
};

Knockout "with" binding, cascading dropdown, reload selected values not working

I have a knockout example, using "With" binding to create a cascading drop-down.
The Drop-down works fine, if i select the values, 4 drop-downs cascading with each corresponding select options.
However I would like to save the drop-down setup, so at a page load, i could get back the saved values, just like presetting the values.
Logging out the values the observables get by calling 'save', after selecting from drop-down. But doesn't work when calling 'loadPresetData', to simulate the data mapping into the observable selected values.
I have forked the fiddle below.
http://jsfiddle.net/turrytheman/3urLenmd/
var sampleModel=[{"products":[{"name":"1948 Porsche 356-A Roadster","year":[{"name":2015,"months":[{"name":"jan"},{"name":"april"},{"name":"dec"}]}]},{"name":"1948 Porsche Type 356 Roadster","year":[{"name":2014,"months":[{"name":"jan"},{"name":"april"},{"name":"dec"}]},{"name":2015,"months":[{"name":"oct"},{"name":"marc"},{"name":"feb"}]}]},{"name":"1949 Jaguar XK 120","year":[{"name":2019,"months":[{"name":"oct"},{"name":"jun"},{"name":"jul"}]},{"name":2013,"months":[{"name":"oct"},{"name":"marc"},{"name":"feb"}]}]}],"name":"Classic Cars"},{"products":[{"name":"1936 Harley Davidson El Knucklehead","year":[{"name":2011,"months":[{"name":"jan"},{"name":"nov"},{"name":"sep"}]}]},{"name":"1957 Vespa GS150","year":[{"name":2014,"months":[{"name":"jan"},{"name":"april"},{"name":"dec"}]},{"name":2015,"months":[{"name":"another"},{"name":"yet"},{"name":"another"}]}]}],"name":"Motorcycles"}];
var Cascading = function() {
var self = this;
self.category = ko.observable();
self.product = ko.observable();
self.years = ko.observable();
self.month = ko.observable();
// Whenever the category changes, reset the product selection
self.category.subscribe(function(val) {
self.product(undefined);
});
self.product.subscribe(function(val) {
self.years(undefined);
});
self.years.subscribe(function(val) {
self.month(undefined);
});
// Operations
self.loadPresetData = function() { //simulating a load, recieved from AJAX, setting saved values
self.category(JSON.parse('{"products":[{"name":"1936 Harley Davidson El Knucklehead","year":[{"name":2011,"months":[{"name":"jan"},{"name":"nov"},{"name":"sep"}]}]},{"name":"1957 Vespa GS150","year":[{"name":2014,"months":[{"name":"jan"},{"name":"april"},{"name":"dec"}]},{"name":2015,"months":[{"name":"another"},{"name":"yet"},{"name":"another"}]}]}],"name":"Motorcycles"}'));
self.product(JSON.parse('{"name":"1936 Harley Davidson El Knucklehead","year":[{"name":2011,"months":[{"name":"jan"},{"name":"nov"},{"name":"sep"}]}]}'));
self.years(JSON.parse('{"name":2015,"months":[{"name":"jan"},{"name":"april"},{"name":"dec"}]}'));
self.month(JSON.parse('{"name":"april"}'));
}
self.save = function() {
var data = {"category": ko.toJSON(ko.toJS(self.category)),
"product": ko.toJSON(ko.toJS(self.product)),
"years": ko.toJSON(ko.toJS(self.years)) ,
"month": ko.toJSON(ko.toJS(self.month))
}
console.log(data);
};
};
ko.applyBindings(new Cascading());
HTML:
<div class='liveExample'>
<div>
<select data-bind='options: sampleModel, optionsText: "name", optionsCaption: "Select...", value: category'> </select>
</div>
<div data-bind="with: category">
<select data-bind='options: products, optionsText: "name", optionsCaption: "Select...", value: $parent.product'> </select>
</div>
<div data-bind="with: product">
<select data-bind='options: year, optionsText: "name", optionsCaption: "Select...", value: $parent.years'> </select>
</div>
<div data-bind="with: years">
<select data-bind='options: months, optionsText: "name", optionsCaption: "Select...", value: $parent.month'> </select>
</div>
<button data-bind='click: loadPresetData'>Load</button>
<button data-bind='click: save'>Save</button>
<div style="color: red"data-bind="text:'Category :' + ko.toJSON(category)"></div>
<div style="color: green"data-bind="text:'Product :' + ko.toJSON(product)"></div>
<div style="color: blue"data-bind="text:'Year :' + ko.toJSON(years)"></div>
<div style="color: black"data-bind="text:'Months :' + ko.toJSON(month)"></div>
</div>

Short answer: The dropdowns are not getting set because the object you are setting to self.category() and other dropdowns in loadPresetData don't exist in sampleModel (or sampleProductCategories in the fiddle).
Yes, there is an object that looks like and has the same properties and nested arrays as the object JSON.parse() creates, but they are totally different objects. They would fail a Strict Equality Comparison or "=== comparison". You can prove this hypothesis by setting the category and other cascading values from the sampleProductCategories array itself.
self.loadPresetData = function() {
self.category(sampleProductCategories[1]);
self.product(sampleProductCategories[1].products[0]);
self.years(sampleProductCategories[1].products[0].year[0]);
self.month(sampleProductCategories[1].products[0].year[0].months[0]);
};
Now, when category is updated, knockout goes and looks for this object in sampleProductCategories. It exists and hence category won't be set to undefined.
Here's an updated fiddle

using valid field breaks input box; knockoutJS

from http://learn.knockoutjs.com/#/?tutorial=collections
Changing
<td><select data-bind="options: $root.availableMeals, value: meal, optionsText: 'mealName'"></select></td>
to
<td><select data-bind="options: $root.availableMeals, value: name, optionsText: 'mealName'"></select></td>
causes the input box to break. When broken, the surcharge doesn't update when you change the meal, and the default meal name doesn't match the price (always first meal, sometimes second price)
// Class to represent a row in the seat reservations grid
function SeatReservation(name, initialMeal) {
var self = this;
self.name = name;
self.meal = ko.observable(initialMeal);
}
// Overall viewmodel for this screen, along with initial state
function ReservationsViewModel() {
var self = this;
// Non-editable catalog data - would come from the server
self.availableMeals = [
{ mealName: "Standard (sandwich)", price: 0 },
{ mealName: "Premium (lobster)", price: 34.95 },
{ mealName: "Ultimate (whole zebra)", price: 290 }
];
// Editable data
self.seats = ko.observableArray([
new SeatReservation("Steve", self.availableMeals[1]),
new SeatReservation("Bert", self.availableMeals[0])
]);
// Operations
self.addSeat = function() {
self.seats.push(new SeatReservation("", self.availableMeals[0]));
}
}
ko.applyBindings(new ReservationsViewModel());
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<h2>Your seat reservations</h2>
<table>
<thead><tr>
<th>Passenger name</th><th>Meal</th><th>Surcharge</th><th></th>
</tr></thead>
<!-- Todo: Generate table body -->
<tbody data-bind="foreach: seats">
<tr>
<td><input data-bind="value: name" /></td>
<td><select data-bind="options: $root.availableMeals, value: name, optionsText: 'mealName'"></select></td>
<td data-bind="text: meal().price"></td>
</tr>
</tbody>
</table>
<button data-bind="click: addSeat">Reserve another seat</button>
name is a valid field in the SeatReservation, and this for loop is iterating over seat reservations. Why doesn't it just show the person's name, why does it go to the default meal value? Thank you

The first problem, as mentioned above, is that you are trying to assign the value from the dropdown into the name field (this is the portion that is written value: name).
If you wanted to show something different within the dropdown field, you would need to modify the optionsText property, similar to this:
<td><select data-bind="options: $root.availableMeals, value: name, optionsText: 'desiredPropertyNameGoesHere'"></select></td>
This is because the text that is rendered in the dropdown is pulled into the select by the optionsText property. The value binding assigns a value to an observable. The text binding displays a value from an observable. I think what may be happening is that you are confusing the behavior of the text and value bindings. When I first started, I made that mistake as well.
You can see that if you look at your <input> element, which is using the value accessor to pull the reservation's owner name into the field.
<td><input data-bind="value: name"></input></td>
If you were to do this with a different HTML element, such as <span>, you would need to use the following binding setup instead:
<td><span data-bind="text: name"></span></td>
See My Sample to show the difference in the example you have been working on.
I hope that helps to clarify a little of what is going on with the example.

meal is an observable, and value binding requires an observable to put the selected value in it, otherwise, nothing changes after selecting different values

Break down the bindings in the <select>:
options takes an array to populate the drop down
optionsText lets you specify a property of an item to display as the text
value is where you save a selected value

Selected Dropdownlist vaue is not updating in the UI Knockout js

In my application, I am using a drop down list as shown below.
<select id="ddlcurrency" data-bind="options: $root.ddlOppCurrency, optionsText: 'CurrencyCode', optionsValue: 'CurrencyCode', optionsCaption: 'Select..', value: selectedCurrId, valueUpdate: 'change'" class="form-control"></select>
I am having a div in which the selected dropdown value has to be binded.
<div class="col-md-8 value" data-bind="text: (CurrencyID() == '' || CurrencyID() == null || CurrencyID() == undefined) ? '--' : CurrencyID">
I have created a function to bind dropdown list and a function to bind the selected value as shown below.
function ddlOppCurrency(CurrencyCode)
{
this.CurrencyCode = ko.observable(CurrencyCode);
}
function Config(CurrencyID)
{
this.selectedCurrId = ko.observable(CurrencyID);
}
Now, when I change the dropdown list, the selected value is not updating in UI. Can anyone let me know how to achieve this.
Thanks in advance.

knockout multiselect selectedOptions contains values instead of objects

I have a select with the attribute multiple. For each option in the select I want the title attribute set (which shows a tooltip). I also want to retrieve the selected options as an array of objects. I managed to get what I want except for the fact that the selected options doesnt return an array of objects but an array of valueTexts. I can't figure out how I get objects in that array.
This is the code I got so far:
HTML:
<select multiple style="width: 150px;" size=15
data-bind="foreach: options, selectedOptions: selectedOptions">
<option data-bind="text: Name, attr: { 'title': Name}"></option>
</select><br />
<button data-bind="click: showSelectedOptions">Show selection</button>
Javascript:
function Option(id, name){
var self = this;
self.Id = id;
self.Name = name;
}
function ViewModel(){
var self = this;
self.options = ko.observableArray([
new Option(0, "NormalText"),
new Option(1, "AnotherText"),
new Option(2, "WaaaaaaaaaaaaaaaayTooLongText")
]);
self.selectedOptions = ko.observableArray([]);
self.showSelectedOptions = function(){
alert(self.selectedOptions());
//what I would like to have:
//if (self.selectedOptions().length > 0)
// alert(self.selectedOptions()[0].Name);
}
}
ko.applyBindings(new ViewModel());
And the fiddle link for demonstration: http://jsfiddle.net/c63Bb/1/
What do I need to add or change so the array selectedOptions contains objects instead of strings?

Try your html like this
<select
data-bind="
options: options,
selectedOptions : selectedOptions,
optionsText: 'Name',
optionsCaption: 'Choose...'
"
size="5" multiple="true"></select>
Demo
See the console for output
EDITS :
To add attributes to option you need to use optionsAfterRender.
This is available only in version 3.1.0. I noticed your fiddle is using 3.0.0.
<select
data-bind="
options: options,
selectedOptions : selectedOptions,
optionsText: 'Name',
optionsAfterRender: $root.setTitle
"
size="5" multiple="true"></select><br />
<button data-bind="click: showSelectedOptions">Show selection</button>
And create a fnction
self.setTitle = function(option, item) {
option.title = item.Name
}
Demo
Reference
See Note 2

Similar to #MuhammadRaheel, I used optionsAfterRender:
<select data-bind="optionsAfterRender: myFunc, ...">
But I needed to use ko.applyBindingsToNode:
var self.myFunc = function(option, item) {
ko.applyBindingsToNode(option, { attr: { title: 'Tooltip!' } }, item);
}

Use options and optionsText bindings instead of foreach:
<select multiple style="width: 150px;" size=15
data-bind="options: options, optionsText: 'Name', selectedOptions: selectedOptions">
<option data-bind="text: Name, attr: { 'title': Name}"></option>
</select>
Here is demo: http://jsfiddle.net/p5E8y/