Unveiling the Power of KnockoutJS: Displaying HTML Content and Populating

Question

Unveiling the Power of KnockoutJS: Displaying HTML Content and Populating

I am trying to achieve a unique effect using KnockoutJS. Let's consider a basic model:

var Item = function () {
    var self = this;
    self.title = ko.observable("");
};

In addition, I have a ViewModel:

var ItemList = function () {
var self = this;
self.list = ko.observableArray();
}

Now the interesting part begins. In this ViewModel, I receive several blocks of HTML markup. The quantity is unknown. For each block, I need to display the HTML markup immediately:

var blocks = await getBlocks();
$.each(blocks, function (index, value) {
    //At this point (as planned), the blocks should be displayed 
  //together with a rotating loading animation.
    self.list.push(new Item());
});

Following that (still in the ViewModel), I need to retrieve data to fill these blocks:

$.each(self.list(), async function (index, value) {
    var data = await getData("some-url");
   //At this point, the blocks should be filled with data, 
  //and the spinning loading animation should disappear.
    self.list().push(data.results[0].title);
});

And finally, all together:

 var Item = function () {
    var self = this;
    self.title = ko.observable("");
};

var ItemList = function () {
    var self = this;
    self.list = ko.observableArray();
    var blocks = await getBlocks();
    $.each(blocks, function (index, value) {
        self.list.push(new Item());
    });

    $.each(self.list(), async function (index, value) {
        var data = await getData("some-url");
        self.list().push(data.results[0].title);
    });
};
ko.applyBindings(new ItemList());

The HTML for all this complexity appears very straightforward:

<div data-bind="foreach: list">
    <span data-bind="text: title"></span>
</div>

This particular approach does not yield the expected results. I am unsure how to achieve this desired outcome with KnockoutJS. Is it even achievable?

javascript ajax knockout.js

Answer 1

Answer №1

This snippet of code contains an error that needs fixing:

self.list().push(data.results[0].title);

The correct version should be:

value.title(data.results[0].title);

Answer 2

This snippet of code contains an error that needs fixing:

self.list().push(data.results[0].title);

The correct version should be:

value.title(data.results[0].title);

Answer 3

Answer №2

Let's explore an example scenario where:

We have a single call that informs us about the total number of items to be rendered
Each item requires a separate call to fetch the necessary data for rendering its UI

In this setup, each individual item takes charge of loading its own data. This approach simplifies the process of assigning received data to the respective list item, regardless of the order in which it arrives.

The sequence of events during the UI rendering process is as follows:

The initial call to retrieve data for populating the list triggers a loading state with a general message displayed
A placeholder list item is created for each item being fetched. These items initiate their data retrieval process but remain in a loading state until completion
As the individual data retrievals finish one by one, the list elements update with their specific content

const { getProductIdsAsync, getProductAsync } = apiMethods();

function Item(id) {
  this.name = ko.observable(null);
  this.loading = ko.pureComputed(() => !this.name());
  
  getProductAsync(id).then(this.name);
};

Item.fromId = id => new Item(id);

function List() {
  this.items = ko.observableArray([]);
  this.loading = ko.pureComputed(() => !this.items().length);
  
  getProductIdsAsync()
    .then(ids => ids.map(Item.fromId))
    .then(this.items);
}

ko.applyBindings({ list: new List() });
  

// Mocking of some async API, not relevant to question:
function apiMethods() {
  const productCatalogDB = {
    1: "Apples",
    2: "Oranges",
    3: "Bananas"
  };

  const delayed = (f, minT, maxT) => 
    (...args) => 
      new Promise(res => {
        setTimeout(
          () => res(f(...args)),
          minT + Math.random() * (maxT - minT)
        )
      });

  return {
    getProductIdsAsync: delayed(
      () => Object.keys(productCatalogDB), 500, 1200),
    getProductAsync: delayed(
      id => productCatalogDB[id], 500, 1500)
  };
}

.loading {
  opacity: .6;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>

<p data-bind="visible: list.loading">
  Loading catalog ids...
</p>

<ul data-bind="foreach: list.items">
  <li data-bind="css: { loading: loading }, text: name() || 'Loading...'">
    
  </li>
</ul>

Answer 4

Let's explore an example scenario where:

We have a single call that informs us about the total number of items to be rendered
Each item requires a separate call to fetch the necessary data for rendering its UI

In this setup, each individual item takes charge of loading its own data. This approach simplifies the process of assigning received data to the respective list item, regardless of the order in which it arrives.

The sequence of events during the UI rendering process is as follows:

The initial call to retrieve data for populating the list triggers a loading state with a general message displayed
A placeholder list item is created for each item being fetched. These items initiate their data retrieval process but remain in a loading state until completion
As the individual data retrievals finish one by one, the list elements update with their specific content

const { getProductIdsAsync, getProductAsync } = apiMethods();

function Item(id) {
  this.name = ko.observable(null);
  this.loading = ko.pureComputed(() => !this.name());
  
  getProductAsync(id).then(this.name);
};

Item.fromId = id => new Item(id);

function List() {
  this.items = ko.observableArray([]);
  this.loading = ko.pureComputed(() => !this.items().length);
  
  getProductIdsAsync()
    .then(ids => ids.map(Item.fromId))
    .then(this.items);
}

ko.applyBindings({ list: new List() });
  

// Mocking of some async API, not relevant to question:
function apiMethods() {
  const productCatalogDB = {
    1: "Apples",
    2: "Oranges",
    3: "Bananas"
  };

  const delayed = (f, minT, maxT) => 
    (...args) => 
      new Promise(res => {
        setTimeout(
          () => res(f(...args)),
          minT + Math.random() * (maxT - minT)
        )
      });

  return {
    getProductIdsAsync: delayed(
      () => Object.keys(productCatalogDB), 500, 1200),
    getProductAsync: delayed(
      id => productCatalogDB[id], 500, 1500)
  };
}

.loading {
  opacity: .6;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>

<p data-bind="visible: list.loading">
  Loading catalog ids...
</p>

<ul data-bind="foreach: list.items">
  <li data-bind="css: { loading: loading }, text: name() || 'Loading...'">
    
  </li>
</ul>

Unveiling the Power of KnockoutJS: Displaying HTML Content and Populating

Answer №1

Answer №2

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