JML

A JavaScript Markup Languange in JavaScript

JML as described in this article makes it easier to create complex DOM hierarchies.

Creating nested elements like the following can be tedious:

<div id="overlay">
    <div class="overlay__inner">
	<div class="overlay__box">
	    <div class="overlay__hdr">
		<span class="overlay__close-btn">X</span>
		<h3>Sign up</h3>
		<p>The coolest newsletter in town</p>
	    </div>
	    <div class="overlay__content">
		...
	    </div>
	</div>
    </div>
</div>

The JavaScript equivalent goes like this:

var overElem = document.createElement("div");
overElem.id = "overlay";
var overInner = document.createElement("div");
overInner.className = "overlay__inner";
var overBox = document.createElement("div");
overBox.className = "overlay__box";
var overHdr = document.createElement("div");
overHdr.className = "overlay__hdr";
var clsBtn = document.createElement("span");
clsBtn.className = "overlay__close-btn";
var title = document.createElement("h3");
title.innerText = "Sign up";
var subtitle = document.createElement("p");
subtitle.innerText = "The coolest newsletter in town";

// a long while later

overHdr.appendChild(clsBtn);
overHdr.appendChild(title);
overHdr.appendChild(subtitle);
overBox.appendChild(overHdr);
...

Not only it is tedious, it is easy to introduce hard to debug errors.

Simplifying things with JML

Here is how we can solve the same problem with JML:

var overlay = ml("div", { id: "overlay"},
    ml("div", { class: "overlay__inner"},
	ml("div", { class: "overlay__box"}, [
	    ml("div", { class: "overlay__hdr"}, [
		ml("span", {
		    class: "overlay__close-btn",
		    onClick: function() {
			console.log("closing the overlay")
		    },
		}, "X"),
		ml("h3", {}, "Sign up"),
		ml("p", {}, "The coolest newsletter in town"),
	    ]),
	    ml("div", { class: "overlay__content"}, ["more content"]),
	])
    )
);
document.body.appendChild(overlay);

A simple elegant solution that follows a similar hierarchy of the original HTML.

There are two versions.

Version 1 (jml_v1.js)

Version 1 creates DOM elements from the furthest child up to the parent. Then it returns the parent the you can manually append the parent to any Node you like:

var title = ml("h1", { id: "page-title", class: "main-title",}, "Title");
header.appendChild(title);

Version 2 (jml_v2.js)

Version 2 create an temporary virtual DOM that holds the resulting hierarchy.

{
	name: "name",		// string
	props: Object,		// key value object
	children: Object,	// string object or array
}

Then the render(root, result) function is called with the root element and the virtual DOM as parameters. What this allows is to create objects from parent to child, and allows for an onCreate event.

var title = ml("h1", {
	id: "page-title",
	class: "main-title",
	onCreate: () => {
		console.log("title created")
	}, "Title");
render(header, title);