Hands-on with the Marko JavaScript framework

Nancy J. Delong

Innovation in entire-stack, server-facet rendering JavaScript frameworks continues apace. Marko is created beneath the aegis of eBay, who employs it in their e-commerce web site. Marko is intended to be an quick-to-understand and significant-general performance framework.

Ryan Carniato, creator of SolidJS, has been involved in the progress of Marko. He describes it as “built particularly to manage the significant general performance needs of eBay’s platform.” Considering eBay draws 307 million monthly people, Marko can just about certainly manage your use situation.

Marko parts

Let’s commence our exploration of Marko with its component technique. Marko has a person of the most basic component definition and discovery systems still devised. You can see a very simple component definition listed here, a coloration picker. Observe that in the most important index.marko file, there is an HTML element called , together with a house made up of an array of hexidecimal colors. How does Marko obtain the coloration-picker component?

The remedy is that Marko begins at the directory the place the component usage is found, then, beginning at the sibling directories, moves up hunting for a /component directory made up of the required component definition. If no such component is found in that app code, Marko will turn to mounted dependencies and scan them as very well.

Be aware that Marko lookups upward, so that directories in independent branches are not knowledgeable of every other. This gives a kind of scoping for the parts.

In our situation, Marko doesn’t have to appear much, mainly because there is a /parts/coloration-picker/index.marko file. (Marko also will load parts from a file with the component title in the parts directory, or a file inside of the component directory with the component title as folder and file.)

If you appear at the /parts/coloration-picker/index.marko file, you’ll see the coloration-picker component definition proven in Listing 1.

Listing 1. coloration-picker.marko

import getDefaultColors from '../../util/getDefaultColors.js'


    this.condition.selectedColor = coloration


Listing 1 incorporates the most important features of a component. It begins by importing yet another JS file with an import assertion (a very simple JavaScript functionality it will use if no colors are handed in). Subsequent, it defines the JavaScript structures it will want in this situation, a class and a functionality. Very last is the actual template markup, which is principally pulling in two other parts, the header and the footer.

Let’s just take a closer appear at that class definition. It defines two strategies.

Assets input

The initial technique is onInput(). This is a lifecycle technique that receives an input argument, and makes it possible for for modifying the component’s condition (a lot more on condition under).

Observe the input variable. That is a reserved identifier in Marko that resolves to the attributes handed in from the guardian above. Try to remember that the most important component contained a house on the element colors that pointed to a difficult-coded listing of hexidecimal colors. People are now accessed by the little one component by using the input.colors house. Properties are absolutely reactive, meaning the technique will ensure that anything dependent on the props will be updated.

Occasion managing

The next technique on the class is handleColorSelected, which is a customized occasion handler. You can see that handler in use in Listing 1 the place the footer is positioned:

Translation: When the on-coloration-chosen occasion is brought on, simply call the handleColorSelected technique, passing whichever arguments are present.

State in Marko

State in Marko is comparable to React in that it is anticipated to be immutable, meaning that a person will have to assign a new condition to update a single house. Marko does supply a way to drive-set off an update of condition:


Like in other reactive frameworks, condition in Marko types the inner condition of the component. The reactive technique is responsible for carrying out updates of the UI and other values that are dependent on that condition.

Iterating and boosting gatherings in Marko

Now let’s get a appear at how the footer component does two factors: iterates around the coloration props and triggers its on-coloration-chosen occasion.

The code for coloration-picker-footer/index.marko is proven in Listing two.

Listing two. coloration-picker-footer


          on-coloration-chosen("handleColorSelected", coloration)/>


You can see the iteration operate is accomplished with the tag.  The tag can specify its iterator variable with the title inside of the | symbols. In this situation, the iterator is offered the title coloration. The assortment to be iterated around is recognized with the of house, in this situation referring to input.colors handed in from the guardian.

Every single member of the input.colors variable will be output as a div, with entry to the coloration variable. This is comparable in syntax to other frameworks like React.

Emitting gatherings in Marko

Most of the operate of the coloration picking by using click on is handled by the coloration-picker-collection component, which is output inside of the for iterator, together with the coloration house and the handler for on-coloration-chosen.

Listing 3 demonstrates the coloration-picker-collection component.

Listing 3. coloration-picker-collection component


design and style
    width: 25px
    top: 25px
    border-radius: 5px 5px 5px 5px
    exhibit: flex
    flex-course: column
    margin: 5px 0px 0px 5px
    float: left

  on-click on("handleColorSelected")
  design and style=
    backgroundColor: input.coloration

Most of coloration-picker-collection is devoted to defining the layout (i.e., the tiny coloured squares that allow for for clicking a coloration). Below you see CSS as portion of a component’s structure, in the design and style block, which defines the tiny rounded square. Be aware that you can also outline CSS in a independent .css file with the title design and style.css. You can see this latter tactic in the /coloration-picker-collection directory.

In the template markup, recognize the inline design and style that is utilised to set the track record coloration to the hexadecimal coloration set on input.coloration.

Also notice how the on-click on and on-touchstart gatherings are utilised to seize interaction from the user with the coloration square. The occasion is handed to handleColorSelected, which is described at the head of the file. It employs this.emit("coloration-chosen") to hearth a customized coloration-chosen occasion.

Recall that coloration-picker-footer watches for customized gatherings with on-coloration-chosen("handleColorSelected", coloration). Observe the handler is calling handleColorSelected and passing the coloration variable. But the place is this functionality described?

Component definition adaptability

The remedy is it is described in the independent component.js file in the exact same directory, comparable to the independent design and style.css file you saw earlier. The capability to place the discrete pieces of the component into a person file or into independent information (or a combination of both equally) makes it possible for for pleasant adaptability in how you outline parts as they grow from very simple to sophisticated.

Await tag in Marko

Marko also incorporates an tag for managing asynchronous rendering. The tag makes it possible for you to go in a guarantee, and the framework will offer with ready for its outcome and only exhibit it when it becomes obtainable. (This is analogous to the in the same way named component in Svelte.)

The tag simplifies dealing with asynchronous output.

A very simple and shock-free of charge framework

Marko lives up to its guarantee to be very simple to understand. For a person thing, it sports activities only a tiny variety of critical main tags to understand. For yet another, these tags are quite clear-cut and operate in harmony with the basic principle of minimum shock. And Marko is a entire-stack framework, so you are also acquiring server-facet rendering out-of-the-box, with integrations for servers like Express.

Combined with the intuitive component definition technique, bundlers for Webpack and Rollup, and top rated-shelf general performance, Marko can make a sturdy situation to be your following JavaScript framework.

Copyright © 2021 IDG Communications, Inc.

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