KOGrid uses virtual scrolling to render content dynamically. I'm looking for something like that but more generic so it could be used for ul
lists, Bootstrap rows, whatever. I saw something called giga-scroll, but I think it's gone now. The Git is dead.
Has anyone seen a custom binding for dynamic content via virtual scrolling?
A simple solution without using a custom binding:
Fiddler Example: http://jsfiddle.net/adrienne/Y2WUN/
Markup:
<div>
<span data-bind="text: items().length"></span>
<img src="http://rniemeyer.github.com/KnockMeOut/Images/loading.gif" data-bind="visible: pendingRequest" />
</div>
<div id="main" data-bind="foreach: items, event: { scroll: scrolled }">
<div data-bind="text: name"></div>
</div>
ViewModel:
var viewModel = {
items: ko.observableArray([]),
scrolled: function(data, event) {
var elem = event.target;
if (elem.scrollTop > (elem.scrollHeight - elem.offsetHeight - 200)) {
getItems(20);
}
},
maxId: 0,
pendingRequest: ko.observable(false)
};
function getItems(cnt) {
if (!viewModel.pendingRequest()) {
//create fake data to pass to echo service
var entries = [];
for (var i = 0; i < cnt; i++) {
var id = viewModel.maxId++;
entries.push({
id: id,
name: "Name" + id
});
}
viewModel.pendingRequest(true);
$.ajax({
type: 'POST',
url: '/echo/json/',
data: {
json: ko.toJSON(entries),
delay: .1
},
success: function(entries) {
ko.utils.arrayForEach(entries, function(entry) {
viewModel.items.push(entry);
});
viewModel.pendingRequest(false);
},
error: function() {
viewModel.pendingRequest(false);
},
dataType: 'json'
});
}
}
ko.applyBindings(viewModel);
getItems(20);
A different solution using a custom binding scrolling the entire browser window:
http://figg-blog.tumblr.com/post/32733177516/infinite-scrolling-knocked-out.
Fiddler example: http://jsfiddle.net/8x4vG/2/
Use the binding like so:
<div data-bind="foreach: collection">
<div>
<span data-bind="text: $index()"></span>
<span data-bind="text: $data"></span>
</div>
</div>
<div data-bind="scroll: collection().length < 160, scrollOptions: { loadFunc: addSome, offset: 10 }">loading</div>
With a View Model looking something like this:
var viewModel = function(){
this.collection = ko.observableArray([])
var disney = ["Mickey", "Donald", "Daffy", "Hewie", "Dewie", "Lewie"]
var self = this;
this.addSome = function(){
for(var i = 0; i < 40; i++){
self.collection.push(disney[Math.floor((Math.random()*6))])
}
}
this.addSome();
}
The binding implementation:
ko.bindingHandlers.scroll = {
updating: true,
init: function(element, valueAccessor, allBindingsAccessor) {
var self = this
self.updating = true;
ko.utils.domNodeDisposal.addDisposeCallback(element, function() {
$(window).off("scroll.ko.scrollHandler")
self.updating = false
});
},
update: function(element, valueAccessor, allBindingsAccessor){
var props = allBindingsAccessor().scrollOptions
var offset = props.offset ? props.offset : "0"
var loadFunc = props.loadFunc
var load = ko.utils.unwrapObservable(valueAccessor());
var self = this;
if(load){
element.style.display = "";
$(window).on("scroll.ko.scrollHandler", function(){
if(($(document).height() - offset <= $(window).height() + $(window).scrollTop())){
if(self.updating){
loadFunc()
self.updating = false;
}
}
else{
self.updating = true;
}
});
}
else{
element.style.display = "none";
$(window).off("scroll.ko.scrollHandler")
self.updating = false
}
}
}