Knockout observablearray remove by index

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Remove a Value Using Remove Function on Observable Array in KnockoutJS

Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. What I want to know is how to return the index of a array that is an object, based on one of the object variables.

An observableArray exposes a method called indexOfwhich is a wrapper to ko. If you just have something like a key, then KO does have a utility function called ko. However, it returns the item and not the index of it. It would be slightly inefficient to get the object and then call indexOf on it, as you would make two passes through the array.

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You could just write a loop yourself looking for the right item or write a generic function based on ko. Now, you can pass an array, a condition, and you will be returned the index of the first item that matches.

Learn more. Asked 8 years, 8 months ago. Active 2 years, 9 months ago. Viewed 30k times. RP Niemeyer k 17 17 gold badges silver badges bronze badges.

Active Oldest Votes. In your example shouldn't return item. I'm trying do something very close to this and had to had the. Just depends if id is observable or not.

In this case it is not, but sounds like for you it is. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.

Part 8 - Form Fields - Click and Event Binding in Knockout .JS

The Overflow Blog. The Overflow How many jobs can be done at home? Featured on Meta.In today's article I will tell you how to remove a specific value using the "remove" function of an Observable Array in KnockoutJS. The remove function removes data from the Array. We can use the remove function to either remove specific data or we can remove a complete set of data in the Array at once.

First of all you need to add an external Knockout js file into your application, you can either download it from this link: "KnockoutJS" or can download my application that is available at the begiinning of this article in Zip Format and then can use the file attached with this Zip file.

After downloading the file you need to call it in the head section of your application. We can now work on our application. First we will work on the ViewModel. For that you need to add a Script tag under the Body Section and then need to add this code:. In this function I created an object named "self" that will represent the current function.

Then I created an Observable Array named "Trainee "consumption. In that Array I provided three names as default names.

Getting started

Then a function is created named "sortPeople". In that function one more function is created, the remove function, in this remove function I declared to remove that the value that is equal to Mohit. Until now our work on ViewModel is completed so we can move towards the View of our application. Here I had simply created a button that is bound to the sortPeople function, this function is bound to the click event of this button.

Then I created an Unordered List that is bound to the Array "tarinee". So, now what will happen is that at run time all the employees will be seen but as will click on the button then that Name will be removed whose value is provided in the remove function.

But as I click on the button then that value is removed that was declared in the function. Now I am changing the value in the function so that some other value can be removed. Now if you run the code and again click on the button then this output will be seen. View All. Anubhav Chaudhary Updated date, Nov 15 Step 1 First of all you need to add an external Knockout js file into your application, you can either download it from this link: "KnockoutJS" or can download my application that is available at the begiinning of this article in Zip Format and then can use the file attached with this Zip file.

Next Recommended Article. Getting Started With.If you want to detect and respond to changes of a collection of thingsuse an observableArray. To see how you can bind the observableArray to a UI and let the user modify it, see the simple list example. An observableArray just tracks which objects it holds, and notifies listeners when objects are added or removed. If you want your observable array not to start empty, but to contain some initial items, pass those items as an array to the constructor.

For example. Behind the scenes, an observableArray is actually an observable whose value is an array plus, observableArray adds some additional features described below.

So, you can get the underlying JavaScript array by invoking the observableArray as a function with no parameters, just like any other observable. Then you can read information from that underlying array. The indexOf function returns the index of the first array item that equals your parameter.

For example, myObservableArray. The slice function is the observableArray equivalent of the native JavaScript slice function i. Calling myObservableArray. All of these functions are equivalent to running the native JavaScript array functions on the underlying array, and then notifying listeners about the change:. For more details about these observableArray functions, see the equivalent documentation of the standard JavaScript array functions.

This is preferable to sort if you want to leave the observable array in its original order but need to display it in a specific order. The default sort is alphabetical, but you can optionally pass a function to control how the array should be sorted.

Your function should accept any two objects from the array and return a negative value if the first argument is smaller, a positive value is the second is smaller, or zero to treat them as equal. The destroy and destroyAll functions are mainly intended as a convenience for developers using Ruby on Rails:.

The convention in Rails is that, when you pass into an action a JSON object graph, the framework can automatically convert it to an ActiveRecord object graph and then save it to your database. Later, when you submit the JSON object graph to Rails, that item will also be deleted from the database while the other array items will be inserted or updated as usual. In some scenarios, it is useful to programmatically determine if you are dealing with an observableArray.

Knockout provides a utility function, ko. But if an observableArray is changed repeatedly or triggers expensive updates, you may get better performance by limiting or delaying change notifications.

This is accomplished using the rateLimit extender like this:. Although you can subscribe to and access an observableArray just like any other observable, Knockout also provides a super-fast method to find out how an observable array has changed i.

You subscribe to array changes as follows:. Performance is O 1 in most cases, i. Knockout supplies the change log without running any difference algorithm. As shown above, the changes are reported as a list of added and deleted values.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here.

Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Using KnockoutJS, how can I remove an item from an observable array?

I want to be able to click on the listitem, and remove the item from the array and thereby the list. There are many ways to ensure that removeExpertise is called with the appropriate value for this. An easy way is to use.

Also, you will want expertise to be an observableArray rather than an observableas an observableArray exposes array manipulation methods including a remove function. Learn more. KnockoutJS remove item from observable array.

knockout observablearray remove by index

Item is listitem within ul, which was generated by foreach Ask Question. Asked 7 years, 11 months ago. Active 5 years, 10 months ago. Viewed 24k times. The code sample below reports: 'this.

Do I need to define some sort of expertise object, and then call it from within there? Hoppe Hoppe 5, 12 12 gold badges 44 44 silver badges 96 96 bronze badges. Active Oldest Votes. It would look like: this. In this case, you want it to always use the instance of AppViewModel as this. Hope that makes sense. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

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Technical site integration observational experiment live on Stack Overflow. Linked 0.This article explains how to dynamically remove data from an Observable Array. In my previous article you learned how to dynamically add new data to an Observable Array and how to make a data editable using Knockoutjs in an ASP. NET Application. This article explains how to dynamically remove the data from the Observable Array.

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First of all we will work on the View Model where a function will remove the data from the array. So let's see the code for that. In the function "x " we create a class that will store the Buyer Name with the Car Selection made by him. Notice that the "feature" property is made observable. After that a new function "y " is created in which the Car Name and it's prices are declared under the carModel and after that in the "self. The "self. For making a new entry in the array we need to push the new entry into the cars array, this is done by the following code:.

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You can see that for adding new data in the array I used "push " but for removing the data we will use "remove ". For removing the data I created a function named "removeCar" as in the following:. Until now our work on the View Model is completed. Now we will work on the View Model so that something can be provided for the removeCar function to work. Step 2. At the end I had taken a button to which addCar is bound, it's click will make a new entry in the array.

Now let's look at the output, when you run the application, this type of window will be available:. After that I added two new rows of data dynamically by clicking on the "Add" button. Then I click on the "Remove" link present in the front of Rows and you can see that Raw is removed. View All. Anubhav Chaudhary Updated date, Nov 27 Introduction In my previous article you learned how to dynamically add new data to an Observable Array and how to make a data editable using Knockoutjs in an ASP.

Step 1 First of all we will work on the View Model where a function will remove the data from the array. For removing the data I created a function named "removeCar" as in the following: self. Next Recommended Article. NET knockoutjs Observable Array.

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Getting Started With.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Other than using the wrong property name, developerexampledata instead of myObservableArrayyour code is just fine.

This could simply be down to you trying to access the first item of an array before the array has been populated. How are we doing? Please help us improve Stack Overflow. Take our short survey. Learn more. How do I access an object by index in a knockout observablearray? Ask Question. Asked 6 years, 11 months ago. Active 4 years, 2 months ago. Viewed 14k times. What's the correct syntax for doing this?

Edit: Fixed a copy and paste error pointed out below. Eric Eric 2 2 gold badges 4 4 silver badges 8 8 bronze badges. That's how you do it. If it's not working, you have some other issue with your code. Active Oldest Votes. Here is a working fiddle.

knockout observablearray remove by index

Kyeotic Kyeotic Yeah that was a copy and paste error when I made the question, my bad. I appreciate the fiddle though; at least I know I've got the syntax right and my problem lay elsewhere. I'll accept your answer and dig in a bit more to figure out where else I might be going wrong. Mattl Mattl 1, 3 3 gold badges 19 19 silver badges 49 49 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I'm designing a quiz with Knockoutjs. I want to display only one question at a time.

I was thinking about a global count var which is added by 1 each time a question is answered. However I can't seem to find a way to get only one question at the time. How would I best approach this?

I'm new to Knockoutjs. I tried questions [number] but that didn't seem to work. Jsfiddle is being funny so I can't post the code there, but it's quite simple: you were almost there! Here's a little push. First, is not really good practice to call the methods in the markup unless necessary, and giving parameters to the function probably means you can use an observable for that.

knockout observablearray remove by index

In this case:. As you can see, in the markup I'm only putting the variable, not calling it out in the form filteredQuestions. By now you may be asking, "What's up with that foreach? I only want to display one question, not all of them. And what's up with the filtered thing? Here's what I'm doing: instead of displaying the original questions array, I'm displaying a filtered one, that gets updated every time any observables inside it changes. Here's the code for the filteredQuestions.

If you pay attention to the code, I'm only returning one array with one question only, the one which Id is the same as the one set up by the currentQuestionId variable.

Nicholas geib (njg)

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