bel

A simple library for composable DOM elements using tagged template strings.

If you're looking for a higher level front end framework, try yo-yo. Or even higher than that, try choo.

usage

For a more in depth tutorial on getting started, please check out the wiki.

note

Please use yo-yoify which will transform any Function.caller into plain strings until an alternative solution to identify element creators is implemented.

yo-yoify can resolve the error like below:

TypeError: Function.caller used to retrieve strict caller

TypeError: access to strict mode caller function is censored

A Simple Element

Create an element:

// list.js 
var bel = require('bel')
 
module.exports = function (items) {
  return bel`<ul>
    ${items.map(function (item) {
      return bel`<li>${item}</li>`
    })}
  </ul>`
}

Then pass data to it and add to the DOM:

// app.js 
var createList = require('./list.js')
var list = createList([
  'grizzly',
  'polar',
  'brown'
])
document.body.appendChild(list)

Data Down, Actions Up

// list.js 
var bel = require('bel')
 
// The DOM is built by the data passed in 
module.exports = function (items, onselected) {
  function render () {
    return bel`<ul>
    ${items.map(function (item) {
      return bel`<li>${button(item.id, item.label)}</li>`
    })}
    </ul>`
  }
  function button (id, label) {
    return bel`<button onclick=${function () {
      // Then action gets sent up 
      onselected(id)
    }}>${label}</button>`
  }
  var element = render()
  return element
}

// app.js 
var bel = require('bel')
var morphdom = require('morphdom')
var list = require('./list.js')
 
module.exports = function (bears) {
  function onselected (id) {
    // When a bear is selected, rerender with the newly selected item 
    // This will use DOM diffing to render, sending the data back down again 
    morphdom(element, render(id))
  }
  function render (selected) {
    return bel`<div className="app">
      <h1>Selected: ${selected}</h1>
      ${list(bears, onselected)}
    </div>`
  }
  // On first render, we haven't selected anything 
  var element = render('none')
  return element
}

lifecycle events

Use the onload and onunload properties to call a function when the element is inserted and removed from the DOM respectively.

var bel = require('bel')
 
var modal = bel`<div onload=${function (element) {
  console.log('Hello DOM!')
}} onunload=${function (element) {
  console.log('Goodbye DOM!')
}}>hello!</div>`
 
document.body.appendChild(modal)
document.body.removeChild(modal)

use with/without hyperx

hyperx is built into bel but there may be times when you wish to use your own version or implementation of hyperx. Or if you prefer to create elements using bel without using tagged template literals:

var createElement = require('bel').createElement
var hyperx = require('hyperx')
var bel = hyperx(createElement)
 
var element = bel`<div class="heading">Hello!</div>`
 
// ... 
 
var sameElement = createElement('div', { className: 'heading' }, ['Hello!'])

security

bel sets attributes with element.setAttribute() and element.setAttributeNS(), and creates text nodes with document.createTextNode(). These approaches mitigate some Cross-Site Scripting (XSS) attacks. You should still code carefully every time you put content from users in the DOM.

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