Hansel

Runner of JavaScript handlers and enhancers

• Lightweight (less than 1kb minified and gzipped)
• Transpile to desired browser target
• No dependencies (except a minor utility function)

Based on the article "Progressive enhancement with handlers and enhancers" by Hidde de Vries. We've been using this model for many years with great pleasure, fine-tuning here and there. Read the article for a deeper explanation.

Built with ❤️ by GRRR.

Installation

$ npm install @grrr/hansel

Note: depending on your setup additional configuration might be needed, since this package is published with untranspiled JavaScript.

Usage

Import into your main JavaScript file:

import { enhance, handle } from '@grrr/hansel';

enhance(document.documentElement, {
  enhancer1(elm) {
    // Enhance elements with this enhancer.
  },
  enhancer2(elm) { /* */ },
  enhancerN(elm) { /* */ },
});

handle(document.documentElement, {
  handler1(elm, event) {
    // Handle clicks on elements with this handler.
  },
  handler2(elm, event) { /* */ },
  handlerN(elm, event) { /* */ },
});

In a more modular setup, this would look like:

import { enhance, handle } from '@grrr/hansel';
import { enhancer as fooEnhancer, handler as fooHandler } from './foo';
import { enhancer as barEnhancer, handler as barHandler } from './bar';

enhance(document.documentElement, {
  fooEnhancer,
  barEnhancer,
});

handle(document.documentElement, {
  fooHandler,
  barHandler,
});

Enhancers

The enhance function will look for DOM nodes containing the data-enhancer attribute. The second argument is a lookup table for enhancer functions. The value of the data-enhancer attribute will be matched with the table and if found, executed, given the element as first argument:

// Given <p data-enhancer="foo" data-message="Hello!"></p>

enhance(document.documentElement, {
  foo(elm) {
    console.log(elm.getAttribute('data-message')); //=> "Hello!"
  }
});

Multiple enhancers are possible by comma-separating them:

<div data-enhancer="foo,bar"></div>

Handlers

Handlers are called on click, using a global event listener on the document.

// Given <button data-handler="shout" data-message="Hello!">shout</button>

handle(document.documentElement, {
  shout(elm, e) {
    alert(elm.getAttribute('data-message')); //=> "Hello!"
    e.preventDefault();
  }
});

Multiple handlers are possible by comma-separating them:

<a data-handler="foo,bar" href="/">Do the thing</a>

Options

It's possible to register a handler with options. To do so, register the handler via an object with an fn and options key:

handle(document.documentElement, {
  foo(elm, e) { /* */ },
  bar(elm, e) { /* */ },
  baz: {
    fn: baz(el, e) {
      // The handler function.
    },
    options: {
      // The handler options.
    },
  },
});

The following options are available:

allowModifierKeys

By default, modifier-clicks (metaKey, ctrlKey, altKey and shiftKey) on anchors (<a>) are caught, and are not passed on to the handler. To disable this behaviour, register the handler with the allowModifierKeys option:

options: {
  allowModifierKeys: true,
},

Furthermore

Thanks to the global click listener, handlers do not have to be re-initialized to dynamically added content. The presence of a data-handler attribute is enough.

Enhancers are run immediately however, so you might want to run them again, for instance when loading new DOM nodes in response to an AJAX call. The first argument to enhance is the container element within which nodes are searched. Therefore, you can pass the parent to the newly created nodes as reference to enhance all its children:

const myContainer = document.querySelector('foo');
myContainer.innerHTML = htmlContainingEnhancedElements;

enhance(myContainer, myEnhancers);