Happy

A few helper/wrapper functions to simplify Hyperapp code.

Install

npm install --save @gjmcn/happy

Hyperapp is included in Happy.

Import

E.g. from CDN:

import {h, u, ur, app, memo} from 'https://cdn.skypack.dev/@gjmcn/happy';

Example

The To Do app from the Hyperapp README using Happy functions:

<script type="module">
  import {u, app, main, h1, input, ul, li, button} from "https://cdn.skypack.dev/@gjmcn/happy";
    
  const AddTodo = u('todos', s => {
    s.todos.push(s.value);
    s.value = '';
  });

  const NewValue = u((s, event) => {
    s.value = event.target.value;
  });

  app({
    init: {todos: [], value: ''},
    view: s => main(
      h1('To do list'),
      input({type: 'text', oninput: NewValue, value: s.value}),
      ul(s.todos.map(todo => li(todo))),
      button({onclick: AddTodo}, 'New!'),
    )
  })
</script>

Usage

Elements

The virtual node function h has parameters tag, props, child_0, child_1, child_2, ... However:

• If props is a string, array, or virtual node, it is actually used as child_0 and an empty object is used for props.

• child_ arguments that are arrays are flattened (nesting is removed) and spread into separate arguments.

• Only tag is required.

Happy also includes element functions for most HTML and SVG elements (see index.js for the full list). These functions are like h without the tag parameter:

p('Some text');
p({class: 'some-class'}, 'Some text');
input({type: 'range'});

Import element functions along with other Happy functions. E.g.

import {u, app, div, p, span} from 'happy';

Text

h automatically applies Hyperapp's text function to child elements that are strings, so the text function is not used explicitly:

// hyperapp
h('div', {}, text('Hello'));

// happy
div('Hello');

Updates

The u function creates an update: an action where we mutate the state directly. u is passed a function f which has state and (optionally) payload parameters. u returns a new function which also has state and payload parameters. The new function shallow copies the state, calls f with the copied state and payload, and returns the copied state.

For brevity, we call the state parameter s rather than state, and typically use s explicitly when accessing state properties (rather than destructuring).

// hyperapp (increase count property by 1)
const Increment = state => ({...state, count: state.count + 1});

// happy
const Increment = u(s => s.count++);

// hyperapp (set user property to name)
const SetUser = (state, name) => ({...state, user: name});

// happy
const SetUser = u((s, name) => s.user = name);

When updating one or more properties that are themselves objects or arrays, we can tell u to shallow copy these properties (as well as the state) by passing the property names as arguments. The function is passed after the property names:

// hyperapp (toggle element of highlight property)
const ToggleHighlight = (state, index) => {
  const highlight = [...state.highlight];
  highlight[index] = !highlight[index];
  return {...state, highlight};
};

// happy
const ToggleHighlight = u('highlight', (s, index) => {
  s.highlight[index] = !s.highlight[index];
})

The ur function is the same as u except that the new function returns whatever f (the passed function) returns. Use ur for an action that modifies the state and returns [ModifiedState, ...Effects].

Notes:

• When using u, no special action is required when the state is an array — unlike with standard actions. (There is no reason to use ur to only return the modified state, but if this is done and the state is an array, the state must be wrapped in another array.)

• u and ur only shallow copy the state and the specified top-level properties. If any other properties are to be mutated, manually shallow copy them inside f.

• u and ur are just convenience functions for creating actions. Standard actions can be used as normal.

The app Function

app is used as in Hyperapp except that:

• The node property can be a DOM element (as in Hyperapp) or a CSS query string — the app is inserted into the first corresponding element. If the node property is absent or falsy, the app is appended to the end of the document body.

• The init option is not required: if init is omitted, null or undefined, the initial state is an empty object. (As normal with Hyperapp, if the initial state is an array, it must be wrapped in another array, e.g. [[4, 5, 6]] or [[4, 5, 6], someEffect].)