Run external function when knockout component is created

Question

I am trying to create new component in knockout:

ko.components.register("categories", {
    viewModel: {
        instance: MY_VIEW_MODEL
    },
    template: require('html-loader?interpolate!./components/categories.html')
});

and my HTML block inside of categories.html:

<div class="panel" data-bind="foreach: categories, afterRender: ${require('../effects.js').fadePanels()}"></div>

and inside of effect.js:

function fadePanels() {
    $('.panel').velocity('fadeInPanels', {
        stagger: 250,
    })
}

plus webpack.config.js:

    test: /\.html$/,
    loader: 'html-loader',
    options: {
        interpolate: true
    },
    exclude: /node_modules/

but it's not working at all. Here is the output from browser (no errors in console):

Do you have any experience with this? Do you know how to correctly handle that?

score 1 · Accepted Answer · answered Oct 15 '18 at 16:42

You can run a function that takes a component's element by using the createViewmodel factory method. This function receives an info object that includes the current element.

ko.components.register("category", {
    viewModel: { 
      createViewModel: (params, info) => {
        fadeIn(info.element);
        return { label: "hello world" }
      } 
    },
    template: `<div data-bind="text: label"></div>`
});

const categories = ko.observableArray(["", "", ""]);
const addCat = () => categories.push("");

ko.applyBindings({ categories, addCat  });

function fadeIn(el) {
  el.classList.add("seeThrough");
  setTimeout(
    () => el.classList.add("fadeIn"), 
    200
  );
}

.seeThrough {
  opacity: 0;
  transition: opacity .25s ease-in-out;
}

.fadeIn {
  opacity: 1;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<ul data-bind="foreach: categories">
  <li data-bind="component: { name: 'category' }"></li>
</ul>

<button data-bind="click: addCat">add</button>

For working with components and webpack, you might want to check out this answer I wrote a few days ago. It describes how to configure webpack to work with knockout components.

that's great! but what about the case I already have a view model with all of the categories inside (therefore I put the property instance to share the same model) and I just want to show them with some visual effect? should I still use 'createViewModel(..)' function? let's say I have already something like this in view model: categories = ko.observableArray([new Category("Category 1"), new Category("Category 2")]) and I just want to show the name of the category as unordered list in HTML. — mullen18, Oct 16 '18 at 13:08

Run external function when knockout component is created

1 Answers1