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Web frontend framework in pure Go

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domui: DOM UI framework for Go

Features

  • Pure go code compiled to wasm
    • Utilizing Go's excellent support for static typing and dynamic reflection
    • Runs on any WebAssembly and DOM supported browsers, Electron, etc
  • Dependent reactive system for both view and state management
    • Conceptually unify view component and state management
    • No hooks, redux, recoil, mobx ...
  • Auto and efficient DOM tree updating
    • Based on virtual DOM diff and patch

Prerequisites

  • Go compiler 1.16 or newer
  • If you are not familiar with compiling and running WebAssembly program, please read the official wiki

Table of contents

package main

import (
	"github.com/reusee/domui"
	"syscall/js"
	"time"
)

// ergonomic aliases
var (
	Div = domui.Tag("div")
	T   = domui.Text
)

// A type to hold all definitions
type Def struct{}

// define the root UI element
func (_ Def) RootElement() domui.RootElement {
	// same to <div>Hello, world!</div>
	return Div(T("Hello, world!"))
}

func main() {
	domui.NewApp(
		// render on <div id="app">
		js.Global().Get("document").Call("getElementById", "app"),
		// pass Def's methods as definitions
		domui.Methods(new(Def))...,
	)
	// prevent from exiting
	time.Sleep(time.Hour * 24 * 365 * 100)
}

The definition of RootElement can be refactored to multiple dependent components.

package main

import (
	"github.com/reusee/domui"
	"syscall/js"
	"time"
)

var (
	Div = domui.Tag("div")
	T   = domui.Text
)

type (
	Def  struct{}
	Spec = domui.Spec
)

// A string-typed state
type Greetings string

// define Greetings
func (_ Def) Greetings() Greetings {
	return "Hello, world!"
}

// A UI element
type GreetingsElement Spec

// define GreetingsElement
func (_ Def) GreetingsElement(
	// use Greetings
	greetings Greetings,
) GreetingsElement {
	return Div(T("%s", greetings))
}

// The root UI element
func (_ Def) RootElement(
	// use GreetingsElement
	greetingsElem GreetingsElement,
) domui.RootElement {
	return Div(
		greetingsElem,
	)
}

func main() {
	domui.NewApp(
		js.Global().Get("document").Call("getElementById", "app"),
		domui.Methods(new(Def))...,
	)
	time.Sleep(time.Hour * 24 * 365 * 100)
}

Definitions can be updated. All affected definitions will be re-calculated recursively till the RootElement.

package main

import (
	"github.com/reusee/domui"
	"syscall/js"
	"time"
)

var (
	Div     = domui.Tag("div")
	T       = domui.Text
	OnClick = domui.On("click")
)

type (
	Def    struct{}
	Spec   = domui.Spec
	Update = domui.Update
)

type Greetings string

func (_ Def) Greetings() Greetings {
	return "Hello, world!"
}

type GreetingsElement Spec

func (_ Def) GreetingsElement(
	greetings Greetings,
) GreetingsElement {
	return Div(T("%s", greetings))
}

func (_ Def) RootElement(
	greetingsElem GreetingsElement,
	// use the Update function
	update Update,
) domui.RootElement {
	return Div(
		greetingsElem,

		// when clicked, do update
		OnClick(func() {
			// provide a new definition for Greetings
			update(func() Greetings {
				return "Hello, DomUI!"
			})
		}),
	)
}

func main() {
	domui.NewApp(
		js.Global().Get("document").Call("getElementById", "app"),
		domui.Methods(new(Def))...,
	)
	time.Sleep(time.Hour * 24 * 365 * 100)
}

The above programs demonstrated tag and event usages. Attributes, styles, classes can also be specified.

package main

import (
	"github.com/reusee/domui"
	"syscall/js"
	"time"
)

var (
	Div        = domui.Tag("div")
	Link       = domui.Tag("a")
	Ahref      = domui.Attr("href")
	Sfont_size = domui.Style("font-size")
	T          = domui.Text
	ID         = domui.ID
	Class      = domui.Class
)

type Def struct{}

func (_ Def) RootElement() domui.RootElement {
	return Div(
		Link(
			T("Hello, world!"),
			// id
			ID("link"),
			// class
			Class("link1", "link2"),
			// href attribute
			Ahref("http://github.com"),
			// font-size style
			Sfont_size("1.6rem"),
		),
	)
}

func main() {
	domui.NewApp(
		js.Global().Get("document").Call("getElementById", "app"),
		domui.Methods(new(Def))...,
	)
	time.Sleep(time.Hour * 24 * 365 * 100)
}

To make a reusable element, define it as a function.

package main

import (
	"fmt"
	"github.com/reusee/domui"
	"reflect"
	"strings"
	"syscall/js"
	"time"
)

var (
	Div     = domui.Tag("div")
	T       = domui.Text
	OnClick = domui.On("click")
)

type (
	Def    struct{}
	any    = interface{}
	Spec   = domui.Spec
	Update = domui.Update
	Specs  = domui.Specs
)

// Greetings with name parameter
type Greetings func(name any) Spec

func (_ Def) Greetings(
	update Update,
) Greetings {
	return func(name any) Spec {
		return Specs{
			T("Hello, %s!", name),
			OnClick(func() {
				// when clicked, update the name argument to upper case
				// use reflect to support all string-typed arguments
				nameValue := reflect.New(reflect.TypeOf(name))
				nameValue.Elem().SetString(
					strings.ToUpper(fmt.Sprintf("%s", name)))
				update(nameValue.Interface())
			}),
		}
	}
}

// string-typed states
type (
	TheWorld string
	TheDomUI string
)

// define two types in one function
func (_ Def) Names() (TheWorld, TheDomUI) {
	return "world", "DomUI"
}

func (_ Def) RootElement(
	greetings Greetings,
	world TheWorld,
	domUI TheDomUI,
) domui.RootElement {
	return Div(
		// use Greetings
		Div(
			greetings(world),
		),
		Div(
			greetings(domUI),
		),
	)
}

func main() {
	domui.NewApp(
		js.Global().Get("document").Call("getElementById", "app"),
		domui.Methods(new(Def))...,
	)
	time.Sleep(time.Hour * 24 * 365 * 100)
}

When updating a definition that has no dependency, instead of passing a function, a pointer can be used.

newGreetings := Greetings("Hello!")
update(&newGreetings)
// is the same to
update(func() Greetings {
  return "Hello!"
})

To do something on App inits, define one or more OnAppInit

func (_ Def) InitFoo() domui.OnAppInit {
  // do something
}

func (_ Def) InitBar() domui.OnAppInit {
  // do something
}

To access the DOM element in an event handler, use a js.Value parameter

type Foo Spec

func (_ Def) Foo() Foo {
  retrun Div(
    OnClick(func(elem js.Value) {
      _ = elem.Call("getAttribute", "href").String()
    }),
  )
}

Specs can be cached for reusing

type Article func(title string, content string) Spec

func (_ Def) Article() Article {
  m := domui.NewSpecMap()
  return m(
    // key
    [2]any{title, content},
    // value
    func() Spec {
      return Div( /* ... */ )
    },
  )
}

Some conditional Spec constructors are provided

var (
  A = domui.Tag("a")
  Ahref = domui.Attr("href")
  Sfont_weight = domui.Style("font-weight")
)

type Link func(href string, bold bool) Spec

func (_ Def) Link() Link {
  return func(href string, bold bool) Spec {
    return A(
      // If
      domui.If(href != "", Ahref(href)),
      // Alt
      domui.Alt(bold,
        Sfont_weight("bold"),
        Sfont_weight("normal"),
      ),
    )
  }
}

And loop constructors

type List func(elems []string) Spec

func (_ Def) List() List {
  return func(elems []string) Spec {
    return Div(
      // For
      domui.For(elems, func(s string) Spec {
        return Div(T("%s", s))
      }),
      // Range
      domui.Range(elems, func(i int, s string) Spec {
        return Div(T("%d: %s", i, s))
      }),
    )
  }
}

In react, UI components are declared as classes or functions, and there may be multiple instances of the same class. All component instances form the component tree. In addition to the component tree, a state tree or other state management scheme may be used to hold non-UI data.

In DomUI, all UI and non-UI components are defined as type/value pairs. UI components are just Spec types or function types that returning Spec. This unification greatly reduces the complexity of nearly everything compared to other MVVM frameworks.

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Web frontend framework in pure Go

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