Elem.js

Simple and idiotic lib to build UI components. It's a templating library promoting functionnal composition with the full expressiveness of JavaScript and support for all existing JavaScript libraries. Elem.js is just a quick and dirty experiment to avoid string templates and string concat when modifying the DOM and does not care about performance at all (ie. recreate DOM nodes all the time).

Install

with npm do :

npm install elemjs --save

API

• Elem.el(name, attributes, children) : Create a representation of an HTML element. Children can be a string/number/boolean, an Elem.el, an array of Elem.el or a __asHtml object.
• Elem.sel(name, children) : Create a representation of a simple HTML element
• Elem.vel(name, attributes) : Create a representation of a void HTML element
• Elem.svg(name, attributes, children) : Create a representation of a simple SVG element
• Elem.vsvg(name, attributes) : Create a representation of a void SVG element
• Elem.nbsp(times) : creates a <span> containing one or more  
• Elem.text(value) : creates a <span>value</span>
• Elem.render(elem, container) : render an element to a container in the DOM
• Elem.renderToString(elem) : render an element as an HTML string
• Elem.renderToStaticHtml(elem) : render an element as a pure HTML string
• Elem.component(options) : render a component and return its state. Return a factory function if opts does not contains a container. See the component section for options
• Elem.unmountComponent(node) : unmount an Elem component at a given DOM node
• Elem.componentToString(options) : render a component as an HTML string
• Elem.registerWebComponent(elemName, options) : register a component as a webcomponent. See the webcomponent section for options.
• Elem.predicate(predicate, elem) : return element if predicate is true or undefined if false. Predicate can be a function
• Elem.state(defaultValues) : create a state object. Similar to Backbone models
• Elem.dispatcher() : creates an event dispatcher
• Elem.style(obj) : create an extendable set of CSS inline styles
• Elem.defer(function) : Defers invoking the function until the current call stack has cleared, similar to using setTimeout with a delay of 0
• Elem.defered(function) : return a function that cal Elem.defer(function)
• Elem.Perf : performance measurement tools
  • Elem.Perf.start : enable performance measures
  • Elem.Perf.stop : disable performance measures
  • Elem.Perf.markStart(name) : mark the start of a measure
  • Elem.Perf.markStop(name) : mark the stop of a measure
  • Elem.Perf.collectMeasures : return all collected measures and clear the measures store
  • Elem.Perf.printMeasures : print collected measures and clear the measures store

Dependencies

Elem can be used as a standalone library and that's awesome.

How can I use Elem.js ?

First imports Elem.min.js in your page. Then you will be able to build your first node

var MyAwesomeNode = Elem.el('h1', 'Hello World!');
Elem.render(MyAwesomeNode, '#container');

Of course, you can build much more complicated nodes

var node = Elem.el('div', { className: 'col-md-6' }, [
  Elem.el('h3', 'Hello World!'),
  Elem.el('p', { style: { backgroundColor: 'red' } }, "Lorem ipsum ....")
]);
Elem.render(MyAwesomeNode, '#container');

As you construct the node tree with functions and arrays, it is prettry easy to map and filter model objects to render your components easily (see the Todo List example above).

Attributes use camel case shaped keys, so something like backgroundColor will be rendered as background-color. Also, you can notice that the class attribute is named className. Also, you can provide an object for className value with boolean as values. Every key with a false value will not be rendered.

var shouldDisplayDarkBackground = true;
var shouldDisplayBrightBackground = !shouldDisplayDarkBackground;
Elem.el('div', {
  className: {
    withBackground: true,
    darkBackground: shouldDisplayDarkBackground,
    brighBackground: shouldDisplayBrightBackground
  }
}, 'Hello');

will produce

<div class="with-background dark-background">Hello</div>

As children are just nodes in an array, it is really easy to add or remove elements from your UI. You can also pass undefined elements or functions that can return undefined to not render nodes.

If you want to provide a child as HTML value, just pass an object like {__asHtml: ' ;-)'}.

You can also attach callback to event on elements like

function saySomething() {
    alert("Something !");
}
 
var node = Elem.el('div', { className: 'col-md-6' }, [
  Elem.el('h3', 'Hello World!'),
  Elem.el('button', {
      className: ['btn', 'btn-primary'],
      onclick: saySomething
    }, 'Say something'),
  Elem.el('p', { style: { backgroundColor: 'red' } }, "Lorem ipsum ....")
]);
Elem.render(MyAwesomeNode, '#container');

And no, the output WILL NOT BE

<div class="col-md-6">
  <h3>Hello World</h3>
  <button class="btn btn-primary" onclick="saySomething">Say Something</button>
  <p style="background-color: red;">Lorem ipsum ....</p>
</div>

but the following with an event listener on the root element of the component listening to click events on the button.

<div class="col-md-6">
  <h3>Hello World</h3>
  <button class="btn btn-primary">Say Something</button>
  <p style="background-color: red;">Lorem ipsum ....</p>
</div>

Supported events are

wheel scroll touchcancel touchend touchmove touchstart click doubleclick
drag dragend dragenter dragexit dragleave dragover dragstart drop
change input submit focus blur keydown keypress keyup copy cut paste

SVG

You can also simply use SVG with Elem.js, using the dedicated API :

function svg() {
  return Elem.svg('svg', { xmlns: Elem.svgNS, version: "1.1", width: "300", height: "200" }, [
    Elem.svg('title', 'Simple SVG pict'),
    Elem.svg('desc', "A rectangle, a line and a circle"),
    Elem.vsvg('rect', { width: 100, height: 80, x: 0, y: 70, fill: "green" }),
    Elem.vsvg('line', { x1: "5", y1: "5", x2: "250", y2: "95", stroke: "red" }),
    Elem.vsvg('circle', { cx: "90", cy: "80", r: "50", fill: "blue" }),
    Elem.svg('text', { x: "180", y: "60" }, 'A text')
  ]);
}
Elem.render(svg, document.getElementById("svg"));

Can I create reusable components ?

Of course you can. You just need to to something like

var timer = Elem.component({
    container: '#timer',
    init: function(state, props) {
        state.set({time: 0});
        setInterval(function() {
            state.set({time: state().time + 1});
        }, 1000);
    },
    render: function(state, props) {
        return Elem.el('span', 'Elapsed : ' + state().time));
    }
});

when creating a component, you can define

{
    container: 'the container where the component will be rendered. Can be omitted to use it as a factory'
    init: 'init function that receive the state and props as parameters'
    initialState: 'function that returns the initial state state of the component. If undefined, an empty one will be created'
    defaultProps: 'function that returns the initial properties for the component, can be passed at instanciation if factory mode'
    render: 'function that will return an Elem node'
}

you can pass an external with Elem.state({...}). Each time the state is changed, the render function will be called and the components will be re-rendered. You can avoid that by using state.set(obj, true).

You can use Elem.component as a component factory like :

 
var Hello = Elem.component({
    // it's a factory because no container is provided
    render: function(state, props) {
        return Elem.el('div',
            [
                Elem.el('h3', "Hello " + props.name + "!")
            ]
        );
    }
});
 
Hello({ name: "World" }).renderTo('#hello'); // render inside #hello div
Hello({ name: "World" }).renderToString();
Hello({ name: "World" }).renderToStaticHtml();
 

You can also use a component into a tree of elements by using a component factory like :

 
var InnerComponent = Elem.component({
    // it's a factory because no container is provided
    render: function(state, props) {
        return Elem.el('div',
            [
                Elem.el('h3', "Hello " + props.name + "!")
            ]
        );
    }
});
 
Elem.component({
    container: '#inner',
    render: function(state, props) {
        return Elem.el('div', [
            Elem.el('h3', 'Inner component demo'),
            InnerComponent({ name: "World" })
        ]);
    }
});
 

The component(props) function returns a function (if you don't provide a container) that you can call to create component that will be rendered in the element tree. The main advantage of using component as factory is that when you change the state of the inner component, only that component will be re-rendered instead of the whole root component and its children.

But, how can I get an actual DOM node from inside my component ?

That's pretty easy, you just have to use refs. Refs give you access to any node inside your component that has been marked with a ref parameter.

 
function MyComponent(state, props, context) {
 
  function clickMe() {
    console.log(context.refs.myInputText.getDOMNode().value);
  }
 
  return Elem.el('div', [
    Elem.el('input', { type: 'text', ref: 'myInputText', value: 'Hello World!' }, []),
    Elem.el('button',
      { type: 'button', className: 'btn btn-primary', onclick: clickme },
      'Click me !!!')
  ]);
}
 
Elem.component({
  container: '#test',
  render: MyComponent
});

You can also get the root DOM node by using context.getDOMNode().

But, I like jsx syntax, how can I use it ?

If you use babel, add jsxPragma=Elem.jsx to options.

var Elem = require('elemjs');
 
Elem.render(
  <h1>Hello jsx</h1>,
  document.body
);

Very simple, isn't it?

But you can't render that stuff server side (isomorphic apps), right ?

Actually you can and it's pretty easy.

First you can use Elem.renderToString or Elem.renderToStaticHtml on any Elem.el node you want.

But you can also do the same on components, let's write a funny clock component;

module.exports = Elem.component({
    init: function(state, props) {
      function update() {
        state.set({
          seconds: (moment().seconds() % 60) * 6,
          minutes: (moment().minutes() % 60) * 6,
          hours: (moment().hours() % 12) * 30,
        });
      }
      update();
      setInterval(update, 1000);
    },
    render: function(state, props) {
        return Elem.el('div', { className: 'circle'}, [
                Elem.el('div', { className: 'hour',
                    style: { transform: 'rotate(' + state().hours + 'deg)' }}, ''),
                Elem.el('div', { className: 'minute',
                    style: { transform: 'rotate(' + state().minutes + 'deg)' }}, ''),
                Elem.el('div', { className: 'second',
                    style: { transform: 'rotate(' + state().seconds + 'deg)' }}, ''),
                Elem.el('span', { className: 'centered' },
                    moment().hours() + ' h ' + moment().minutes() + ' m ' + moment().seconds() + ' s')
            ]
        );
    }
});

Now we can instanciate it on the server side, and render it as an HTML string :

var express = require('express');
var app = express();
var Clock = require('./clock');
 
app.get('/clock.html', function (req, res) {
  var clock = Clock(); // instanciate a component
  res.send(clock.renderToString());
  // or you can consider the following code for a pure html output
  // clock.renderToStaticHtml
});
 
var server = app.listen(3000, function () {
  var host = server.address().address;
  var port = server.address().port;
  console.log('Clock app listening at http://%s:%s', host, port);
});

on the client side, you just have to re-render the component at the same div dans Elem while re-attach itself generated DOM.

What about webcomponents ?

You can use an Elem component to create webcomponent. To do that, just write something like (don't forget the dash in the component name)

Elem.registerWebComponent('todo-list', {
    init: function(state, props) {
      state.set({
        key: _.uniqueId('todolist-'),
        tasks: [],
        text: ''
      });
      props.componentsBus.on('otherWebComponentClicked', function(evt) {
        ...
      });
      props.componentsBus.trigger('todoListLoaded', { tasks: state().tasks });
    },
    render: TodoApp
});

and use it like

<div>
  <todo-list></todo-list>
</div>

when creating a webcomponent, you can define options like

{
    init: 'init function that receive the state and props as parameters'
    initialState: 'function that returns the initial state state of the component. If undefined, an empty one will be created'
    defaultProps: 'function that returns the initial properties for the component, can be passed at instanciation if factory mode'    render: 'function that will return an Elem node'
}

Properties of the webcomponent are defined with the HTML tag attributes. You can use a renderOnly="true" attribute to not redraw the webcomponent all the time. You can also use noshadow="false" to avoid rendering the component inside the shadow root of the webcomponent.

Now let's write a more complicated component : The Todo list

function NewTask(state, props) {
  function deleteAllDone() {
      var tasks = _.filter(state().tasks, function(item) {
          return item.done === false;
      });
      state.set({tasks: tasks});
  }
  function createNewTask() {
      var tasks = state().tasks;
      if (state().text !== '') {
          tasks.push({
              _id: _.uniqueId('task_'),
              name: state().text,
              done: false
          });
          state.set({
            text: '',
            tasks: tasks
          });
      }
  }
  function storeName(e) {
      var text = e.target.value;
      state.set({text: text}, true); // silent set
      if (e.keyCode === 13) {
          createNewTask();
          e.preventDefault();
      }
  }
  return Elem.el('div',
      Elem.el('div', { className: 'row' }, [
          Elem.el('form', { role: 'form' }, [
              Elem.el('div', { className: ['form-group', 'col-md-10'] },
                  Elem.el('input', {
                      dataKey: state().key,
                      onchange: storeName,
                      value: state().text,
                      placeholder: 'What do you have to do ?',
                      type: 'text', className: 'form-control',
                  }, [])
              ),
              Elem.el('div', { className: 'form-group' },
                  Elem.el('div', { className: 'btn-group' }, [
                      Elem.el('button', {
                              type: 'button',
                              className: 'btn btn-success',
                              onclick: createNewTask
                          },
                          Elem.el('span', {
                              className: 'glyphicon glyphicon-floppy-saved'
                          }, [])
                      ),
                      Elem.el('button', {
                              onclick: deleteAllDone,
                              type: 'button',
                              className: 'btn btn-danger'
                          },
                          Elem.el('span', { className: 'glyphicon glyphicon-trash' }, [])
                      )
                  ])
              )
          ])]
      )
  );
}
 
function TaskItem(state, props) {
  function flipTaskState() {
      var tasks = _.map(state().tasks, function(item) {
          if (props.task._id === item._id) {
              var newTask = _.clone(item);
              newTask.done = !props.task.done;
              return newTask;
          }
          return item;
      });
      state.set({tasks: tasks});
  }
  return Elem.el('li', { className: 'list-group-item' },
      Elem.el('div', { className: 'row' }, [
          Elem.el('div', { className: 'col-md-10' }, props.task.name),
          Elem.el('div', { className: 'col-md-2' },
              Elem.el('span', {
                  onclick: flipTaskState,
                  className: {
                      label: true,
                      labelSuccess: props.task.done,
                      labelDefault: !props.task.done
                  },
                  style: {
                      cursor: 'pointer'
                  }
              }, 'Done')
          )
      ])
  );
}
 
function TodoApp(state, props, component) {
  return Elem.el('div', { className: 'col-md-4' }, [
      Elem.el('h3', 'Todo List'),
      NewTask(state, props, component),
      Elem.el('ul', { className: 'list-group' }, _.map(state().tasks, function(task) {
          return TaskItem(state, { task: task}, component);
      }))
  ]);
}
 
Elem.component({
  container: '#container',
  init: function(state, props) {
      state.set({
        tasks: [],
        text: ''
      });
  },
  render: TodoApp
});