HyperApp is a 1kb functional JavaScript library for building modern UI applications.
npm i hyperapp
CDN
<scriptsrc="https://cdn.rawgit.com/hyperapp/hyperapp/master/dist/app.min.js"></script><scriptsrc="https://cdn.rawgit.com/hyperapp/hyperapp/master/dist/html.min.js"></script>Browserify
browserify -g uglifyify index.js | uglifyjs > bundle.js
Counter
app({model: 0,update: {add: model=>model+1,sub: model=>model-1},view: (model,msg)=>html`<div><buttononclick=${msg.add}>+</button><h1>${model}</h1><buttononclick=${msg.sub}disabled=${model<=0}>–</button></div>`})Input
app({model: "",update: {text: (_,value)=>value},view: (model,msg)=>html`<div><h1>Hi${model ? " "+model : ""}.</h1><inputoninput=${e=>msg.text(e.target.value)}/></div>`})Drag and Drop
constmodel={dragging: false,position: {x: 0,y: 0,offsetX: 0,offsetY: 0}}constview=(model,msg)=>html`<divonmousedown=${e=>msg.drag({position: {x: e.pageX,y: e.pageY,offsetX: e.offsetX,offsetY: e.offsetY}})}style=${{userSelect: "none",cursor: "move",position: "absolute",padding: "10px",left: `${model.position.x-model.position.offsetX}px`,top: `${model.position.y-model.position.offsetY}px`,backgroundColor: model.dragging ? "gold" : "deepskyblue"}}>Drag Me!</div>`constupdate={drop: model=>({dragging: false}),drag: (model,{ position })=>({dragging: true, position }),move: (model,{ x, y })=>model.dragging
? ({position: { ...model.position, x, y }})
: model}constsubs=[(_,msg)=>addEventListener("mouseup",msg.drop),(_,msg)=>addEventListener("mousemove",e=>msg.move({x: e.pageX,y: e.pageY}))]app({ model, view, update, subs })Todo
constFilterInfo={All: 0,Todo: 1,Done: 2}constmodel={todos: [],filter: FilterInfo.All,input: "",placeholder: "Add new todo!"}constview=(model,msg)=>{returnhtml`<div><h1>Todo</h1><p> Show: ${Object.keys(FilterInfo).filter(key=>FilterInfo[key]!==model.filter).map(key=>html`<span><ahref="#" onclick=${_=>msg.filter({value: FilterInfo[key]})}>${key}</a></span> `)}</p><p><ul>${model.todos.filter(t=>model.filter===FilterInfo.Done ? t.done :model.filter===FilterInfo.Todo ? !t.done :model.filter===FilterInfo.All).map(t=>html`<listyle=${{color: t.done ? "gray" : "black",textDecoration: t.done ? "line-through" : "none"}}onclick=${e=>msg.toggle({value: t.done,id: t.id})}>${t.value}</li>`)}</ul></p><p><inputtype="text"onkeyup=${e=>e.keyCode===13 ? msg.add() : ""}oninput=${e=>msg.input({value: e.target.value})} value=${model.input} placeholder=${model.placeholder}/><buttononclick=${msg.add}>add</button></p></div>`}constupdate={add: model=>({input: "",todos: model.todos.concat({done: false,value: model.input,id: model.todos.length+1})}),toggle: (model,{ id, value })=>({todos: model.todos.map(t=>id===t.id
? Object.assign({},t,{done: !value})
: t)}),input: (model,{ value })=>({input: value}),filter: (model,{ value })=>({filter: value})}app({ model, view, update })Use html to compose HTML elements.
consthello=html`<h1>Hello World!</h1>`html is a tagged template string. If you are familiar with React, this is like JSX, but without breaking JavaScript.
Use app to create your app. The app function receives an object with any of the following properties.
A value or object that represents the entire state of your app.
To update the model, you send actions describing how the model should change. See view.
An object composed of functions known as reducers. These are a kind of action you send to update the model.
A reducer describes how the model should change by returning a new model or part of a model.
constupdate={increment: model=>model+1,decrement: model=>model-1}If a reducer returns part of a model, that part will be merged with the current model.
You call reducers inside a view, effect or subscription.
Reducers have a signature (model, data), where
modelis the current model, anddatais the data sent along with the action.
The view is a function that returns HTML using the html function.
The view has a signature (model, msg, params), where
modelis the current model,msgis an object you use to send actions (call reducers or cause effects) andparamsare the route parameters.
To send an action
msg.action(data)where data is any data you want to share with the reducer or effect.
Example
app({model: true,view: (model,msg)=>html`<buttononclick=${msg.toggle}>${model+""}</button>`,update: {toggle: model=>!model}})Alternatively, a view can be an object with multiple views. In this case, each view should a key binding it to a route.
Effects cause side effects and are often asynchronous, like writing to a database, or sending requests to servers. They can dispatch other actions too.
Effects have a signature (model, msg, error), where
modelis the current model,msgis an object you use to call reducers / cause effects (see view), anderroris a function you may call with an error if something goes wrong.
Example
constwait=time=>newPromise(resolve=>setTimeout(_=>resolve(),time))constmodel={counter: 0,waiting: false}constview=(model,msg)=>html`<buttononclick=${msg.waitThenAdd}disabled=${model.waiting}>${model.counter}</button>`constupdate={add: model=>({counter: model.counter+1}),toggle: model=>({waiting: !model.waiting})}consteffects={waitThenAdd: (model,msg)=>{msg.toggle()wait(1000).then(msg.add).then(msg.toggle)}}app({ model, view, update, effects })Subscriptions are functions that run once when the DOM is ready. Use a subscription to register global events, like mouse or keyboard listeners.
While reducers and effects are actions you cause, you can't call subscriptions directly.
A subscription has a signature (model, msg, error).
Example
app({model: {x: 0,y: 0},update: {move: (_,{ x, y })=>({ x, y })},view: model=>html`<h1>${model.x}, ${model.y}</h1>`,subs: [(_,msg)=>addEventListener("mousemove",e=>msg.move({x: e.clientX,y: e.clientY}))]})Hooks are functions called for certain events during the lifetime of the app. You can use hooks to implement middleware, loggers, etc.
Example
app({model: true,view: (model,msg)=>html`<div><buttononclick=${msg.doSomething}>Log</button><buttononclick=${msg.boom}>Error</button></div>`,update: {doSomething: model=>!model,},effects: {boom: (model,msg,data,err)=>setTimeout(_=>err(Error("BOOM")),1000)},hooks: {onError: e=>console.log("[Error] %c%s","color: red",e),onAction: name=>console.log("[Action] %c%s","color: blue",name),onUpdate: (last,model)=>console.log("[Update] %c%s -> %c%s","color: gray",last,"color: blue",model)}})Called when the model changes. Signature (lastModel, newModel, data).
Called when an action (reducer or effect) is dispatched. Signature (name, data).
Called when you use the error function inside a subscription or effect. If you don't use this hook, the default behavior is to throw. Signature (err).
The root is the HTML element that will serve as a container for your app. If none is given, a div element is appended to the document.body.
Instead of a view as a single function, declare an object with multiple views and use the route path as the key.
app({view: {"*": (model,msg)=>{},"/": (model,msg)=>{},"/:slug": (model,msg,params)=>{}}})/index route, also used if no other route matches/:a/:b/:cmatches a route with three components using the regular expression[A-Za-z0-9]+and stores each captured group in the params object, which is passed into the view function.
The route path syntax is based in the same syntax found in Express.
Example
const{ app, html }=require("hyperapp")constanchor=n=>html`<h1><ahref=${"/"+n}>${n}</a></h1>`app({view: {"/": _=>anchor(Math.floor(Math.random()*999)),"/:key": (model,msg,{ key })=>html`<div><h1>${key}</h1><ahref="/">Back</a></div>`}})To update the address bar relative location and render a different view, use msg.setLocation(path).
Example
app({view: {"/": (model,msg)=>html`<div><h1>Home</h1><buttononclick=${_=>msg.setLocation("/about")}>About</button></div>`,"/about": (model,msg)=>html`<div><h1>About</h1><buttononclick=${_=>msg.setLocation("/")}>Home</button></div>`}})As a bonus, we intercept all <a href="/path">...</a> clicks and call msg.setLocation("/path") for you. If you want to opt out of this, add the custom attribute data-no-routing to any anchor element that should be handled differently.
<adata-no-routing>...</a>Example
app({view: {"/": (model,msg)=>html`<div><h1>Home</h1><ahref="/about">About</a></div>`,"/about": (model,msg)=>html`<div><h1>About</h1><ahref="/">Home</a></div>`}})