The div boxes in this example are hidden by default using the CSS display property which value is set to none. There are a variety of approaches for adding and removing option elements in a select box using JavaScript. An old-fashioned approach uses an option constructor and array syntax. Both select and options objects provide add and remove methods. But the focus here is on DOM methods due to their solid browser support and flexibility.
Adding and removing models one at a time is all well and good, but sometimes you have so many models to change that you'd rather just update the collection in bulk. Use reset to replace a collection with a new list of models , triggering a single "reset" event on completion, and without triggering any add or remove events on any models. For convenience, within a "reset" event, the list of any previous models is available as options.previousModels. When returning a JSON response, send down the attributes of the model that have been changed by the server, and need to be updated on the client.
When responding to a "read" request from a collection (Collection#fetch), send down an array of model attribute objects. Convenience to create a new instance of a model within a collection. Equivalent to instantiating a model with a hash of attributes, saving the model to the server, and adding the model to the set after being successfully created. If client-side validation failed, the model will be unsaved, with validation errors.
In order for this to work, you should set the model property of the collection. The create method can accept either an attributes hash and options to be passed down during model instantiation or an existing, unsaved model object. Add a model to the collection, firing an "add"event for each model, and an "update" event afterwards.
If a model property is defined, you may also pass raw attributes objects and options, and have them be vivified as instances of the model using the provided options. Pass to splice the model into the collection at the specified index. By default save checks validate before setting any attributes but you may also tell set to validate the new attributes by passing as an option. With Backbone, you represent your data as Models, which can be created, validated, destroyed, and saved to the server. Boundary string | element 'clippingParents' Overflow constraint boundary of the dropdown menu (applies only to Popper's preventOverflow modifier). By default it's 'clippingParents' and can accept an HTMLElement reference .
For more information refer to Popper's detectOverflow docs. Display string 'dynamic' By default, we use Popper for dynamic positioning. DropdownAnimation string 'on' Turn on / off dropdown animation.
Offset array | string | function 0 Offset of the dropdown relative to its target. We can remove the options one by one or by selecting more than one option and then by pressing the button. Here also we will use the similar function like above but before deleting we will check if the option is checked or not.
Selectbox.options.selected will return true if the option is selected. This way we will check all the elements of the list box and if they are checked then we will add the command selectbox.options.remove; to remove that particular option from the list box. We can remove the options from a list box by using client side JavaScript. You can see the article explaining how to add options to a list box using JavaScript. Here we will discuss on how to remove option on selection and removing all the options in one go.
We will use different functions and connect them to buttons to execute them. Here are some functions and there uses in removing the options. I selected the elements using the "getElementsByClassName" function and then iterated through them and deleted them one by one. The problem was that, as I deleted the items they were removed from the HTMLCollection.
Leaving me without any error in the console and without all the elements being removed from the page. Fetch the default set of models for this collection from the server, setting them on the collection when they arrive. The options hash takes success and error callbacks which will both be passed as arguments. When the model data returns from the server, it uses setto merge the fetched models, unless you pass , in which case the collection will be reset. Delegates to Backbone.syncunder the covers for custom persistence strategies and returns a jqXHR.
The server handler for fetch requests should return a JSON array of models. A Model manages an internal table of data attributes, and triggers "change" events when any of its data is modified. Models handle syncing data with a persistence layer — usually a REST API with a backing database. Design your models as the atomic reusable objects containing all of the helpful functions for manipulating their particular bit of data.
Models should be able to be passed around throughout your app, and used anywhere that bit of data is needed. New Rdio was developed from the ground up with a component based framework based on Backbone.js. All of this relies on Backbone's views and models, and all URL routing is handled by Backbone's Router. When data changes are signaled in realtime, Backbone's Events notify the interested components in the data changes. Backbone forms the core of the new, dynamic, realtime Rdio web and desktop applications.
Parse is called by Backbone whenever a collection's models are returned by the server, in fetch. The function is passed the raw response object, and should return the array of model attributes to be addedto the collection. The default implementation is a no-op, simply passing through the JSON response. Override this if you need to work with a preexisting API, or better namespace your responses. Override this property to specify the model class that the collection contains. Save a model to your database , by delegating to Backbone.sync.
Returns a jqXHR if validation is successful and false otherwise. As with set, you may pass individual keys and values instead of a hash. If the model has a validatemethod, and validation fails, the model will not be saved. If the model isNew, the save will be a "create", if the model already exists on the server, the save will be an "update" .
It often renders the data from a specific model, or number of models — but views can also be data-less chunks of UI that stand alone. Instead, views listen to the model "change" events, and react or re-render themselves appropriately. This tutorial shows how to get, add and remove options form a select/dropdown using plain JavaScript.
In this tutorial, you have learned how to add options to and remove options from a select box using JavaScript. All "add" and "remove" events are now sent through the model, so that views can listen for them without having to know about the collection. ToJSON is no longer called at all for 'read' and 'delete' requests. Backbone routes are now able to load empty URL fragments. Backbone.js now supports Zepto, alongside jQuery, as a framework for DOM manipulation and Ajax support. Implemented Model#escape, to efficiently handle attributes intended for HTML interpolation.
When trying to persist a model, failed requests will now trigger an "error" event. The ubiquitous options argument is now passed as the final argument to all "change" events. Walmart used Backbone.js to create the new version of their mobile web application and created two new frameworks in the process. Thorax provides mixins, inheritable events, as well as model and collection view bindings that integrate directly with Handlebars templates.
Perhaps the single most common JavaScript "gotcha" is the fact that when you pass a function as a callback, its value for this is lost. View events are automatically bound to the view's context for you. You may also find it helpful to use _.bind and _.bindAllfrom Underscore.js. Backbone views are almost more convention than they are code — they don't determine anything about your HTML or CSS for you, and can be used with any JavaScript templating library.
The general idea is to organize your interface into logical views, backed by models, each of which can be updated independently when the model changes, without having to redraw the page. Each model can be a Model instance, an id string or a JS object, any value acceptable as the id argument of collection.get. Fires a "remove" event for each model, and a single "update" event afterwards, unless is passed.
The model's index before removal is available to listeners as options.index. Merges the model's state with attributes fetched from the server by delegating to Backbone.sync. Useful if the model has never been populated with data, or if you'd like to ensure that you have the latest server state. Triggers a "change" event if the server's state differs from the current attributes.
Fetch accepts success and error callbacks in the options hash, which are both passed as arguments. Essentially a reducer function takes a state and action as input and returns a new state based on this information as output. In this case, there is only one action type and thus one branch to remove an item. The actual logic to remove the item from the list moved from our handler function into this reducer now. Bootstrap's dropdowns, on the other hand, are designed to be generic and applicable to a variety of situations and markup structures.
For instance, it is possible to create dropdowns that contain additional inputs and form controls, such as search fields or login forms. For this reason, Bootstrap does not expect any of the role and aria- attributes required for true ARIA menus. Authors will have to include these more specific attributes themselves. In the following article, we dynamically add and remove list items using JavaScript.
We are using JavaScript to add and/or remove list items dynamically which means that if we run our webpage it will show the option of adding and removing items using buttons. To remove all option of dropdown box in JavaScript, we can set the options.length property of the select element to 0. Third, register a click event listener to the btnRemove button. In the event listener, we save the selected options in an array first and remove each of them then. There are also multiple ways to dynamically remove options from a select box.
Backbone now has Controllers and History, for doing client-side routing based on URL fragments. Added emulateHTTP to provide support for legacy servers that don't do PUT and DELETE. Added emulateJSON for servers that can't accept application/jsonencoded requests. Added Model#clear, which removes all attributes from a model.
All Backbone classes may now be seamlessly inherited by CoffeeScript classes. Within a collection's add and remove events, the index of the model being added or removed is now available as options.index. Added options.changes to Collection "update" event which includes added, merged, and removed models. When Pandora redesigned their site in HTML5, they chose Backbone.js to help manage the user interface and interactions.
For example, there's a model that represents the "currently playing track", and multiple views that automatically update when the current track changes. The station list is a collection, so that when stations are added or changed, the UI stays up to date. It's common to nest collections inside of models with Backbone. For example, consider a Mailbox model that contains many Message models. One nice pattern for handling this is have a this.messages collection for each mailbox, enabling the lazy-loading of messages, when the mailbox is first opened ... Perhaps with MessageList views listening for "add" and "remove" events.
Backbone is agnostic as to whether you use Underscore templates, Mustache.js, direct DOM manipulation, server-side rendered snippets of HTML, or jQuery UI in your render function. Sometimes you'll have a view that renders thousands of models at once, in a tight loop. Both can be appropriate in the same app, depending on the quantity of data involved, and the complexity of the UI. Uses jQuery's on function to provide declarative callbacks for DOM events within a view.
If an events hash is not passed directly, uses this.eventsas the source. The callback may be either the name of a method on the view, or a direct function body. Omitting the selector causes the event to be bound to the view's root element (this.el). This.el can be resolved from a DOM selector string or an Element; otherwise it will be created from the view's tagName, className, id and attributes properties. If none are set, this.el is an empty div, which is often just fine. An el reference may also be passed in to the view's constructor.
Parse is called whenever a model's data is returned by the server, in fetch, and save. The function is passed the raw response object, and should return the attributes hash to be set on the model. Destroys the model on the server by delegating an HTTP DELETErequest to Backbone.sync. Accepts success and error callbacks in the options hash, which will be passed . Pass if you'd like to wait for the server to respond before removing the model from the collection.
You can deploy, delete, and modify functions using Firebase CLI commands or by setting runtime options in your functions source code. The document.createElement method is used to create an option element. The document.createTextNode method is used to add text to the option. To add a value attribute to the option element, you can use either the setAttribute method or dot syntax. To add the new option element to the end of the list of options, use the appendChild method.
