Reactivity
Declare state
Ember Polaris
import Component from "@glimmer/component";
export default class NameComponent extends Component {
name = "John";
<template>
<h1>Hello {{this.name}}</h1>
</template>
}
Mithril
import m from "mithril";
export default function Name() {
let name = "John";
return {
view: () => m("h1", `Hello ${name}`),
};
}
Update state
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
export default class CounterComponent extends Component {
@tracked name = "John";
constructor(owner, args) {
super(owner, args);
this.name = "Jane";
}
<template>
<h1>Hello {{this.name}}</h1>
</template>
}
Mithril
import m from "mithril";
export default function Name() {
let name = "John";
name = "Jane";
return {
view: () => m("h1", `Hello ${name}`),
};
}
Computed state
Ember Polaris
import Component, { tracked } from "@glimmer/component";
export default class DoubleCount extends Component {
@tracked count = 10;
get doubleCount() {
return this.count * 2;
}
<template>
<div>{{this.doubleCount}}</div>
</template>
}
Mithril
import m from "mithril";
export default function DoubleCount() {
let count = 10;
let doubleCount = count * 2;
return {
view: () => m("div", doubleCount),
};
}
Templating
Minimal template
Ember Polaris
<template>
<h1>Hello world</h1>
</template>
Mithril
import m from "mithril";
export default function HelloWorld() {
return {
view: () => m("h1", "Hello World"),
};
}
Styling
Ember Polaris
<template>
<h1 class="title">I am red</h1>
<button style="font-size: 10rem;">I am a button</button>
<style>
.title {
color: red;
}
</style>
</template>
Mithril
import "./style.css";
import m from "mithril";
export default function CssStyle() {
return {
view: () =>
m(
"div",
m("h1.title", "I am red"),
m("button", { style: { fontSize: "10rem" } }, "I am a button"),
),
};
}
Loop
Ember Polaris
const colors = ["red", "green", "blue"];
<template>
<ul>
{{#each colors as |color|}}
<li>{{color}}</li>
{{/each}}
</ul>
</template>
Mithril
import m from "mithril";
export default function Colors() {
const colors = ["red", "green", "blue"];
return {
view: () =>
m(
"ul",
colors.map((color, idx) => m("li", { key: idx }, color)),
),
};
}
Event click
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
export default class Counter extends Component {
@tracked count = 0;
incrementCount = () => this.count++;
<template>
<p>Counter: {{this.count}}</p>
<button {{on "click" this.incrementCount}}>+1</button>
</template>
}
Mithril
import m from "mithril";
export default function Counter() {
let count = 0;
const incrementCount = () => (count = count + 1);
return {
view: () =>
m(
"div",
m("p", `Counter: ${count}`),
m("button", { onclick: incrementCount }, "+1"),
),
};
}
Dom ref
Ember Polaris
import { modifier } from "ember-modifier";
const autofocus = modifier((element) => element.focus());
<template>
<input {{autofocus}} />
</template>
Mithril
import m from "mithril";
export default function InputFocused() {
let value = "";
return {
view: () =>
m("input", {
oncreate: ({ dom }) => dom.focus(),
type: "text",
value,
oninput: (e) => (value = e.target.value),
}),
};
}
Conditional
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
const TRAFFIC_LIGHTS = ["red", "orange", "green"];
export default class TrafficLight extends Component {
@tracked lightIndex = 0;
get light() {
return TRAFFIC_LIGHTS[this.lightIndex];
}
nextLight = () => {
this.lightIndex = (this.lightIndex + 1) % TRAFFIC_LIGHTS.length;
};
<template>
<button {{on "click" this.nextLight}}>Next light</button>
<p>Light is: {{this.light}}</p>
<p>
You must
{{#if (eq this.light "red")}}
STOP
{{else if (eq this.light "orange")}}
SLOW DOWN
{{else if (eq this.light "green")}}
GO
{{/if}}
</p>
</template>
}
Mithril
import m from "mithril";
const TRAFFIC_LIGHTS = ["red", "orange", "green"];
export default function TrafficLight() {
let lightIndex = 0;
let currentLight = () => TRAFFIC_LIGHTS[lightIndex];
const nextLight = () => (lightIndex + 1) % TRAFFIC_LIGHTS.length;
const instructions = () => {
switch (currentLight()) {
case "red":
return "STOP";
case "orange":
return "SLOW DOWN";
case "green":
return "GO";
}
};
return {
view: () =>
m(
"div",
m("button", { onclick: nextLight }, "Next light"),
m("p", `Light is: ${currentLight()}`),
m("p", "You must ", m("span", instructions())),
),
};
}
Lifecycle
On mount
Ember Polaris
const pageTitle = () => document.title;
<template>
<p>Page title is: {{(pageTitle)}}</p>
</template>
Mithril
import m from "mithril";
export default function PageTitle() {
return {
view: () => m("p", `Page title: ${document.title}`),
};
}
On unmount
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
import { registerDestructor } from "@ember/destroyable";
export default class Time extends Component {
@tracked time = new Date().toLocaleTimeString();
constructor(owner, args) {
super(owner, args);
let timer = setInterval(() => {
this.time = new Date().toLocaleTimeString();
}, 1000);
registerDestructor(this, () => clearInterval(timer));
}
<template>
<p>Current time: {{this.time}}</p>
</template>
}
Mithril
import m from "mithril";
export default function Time() {
let time = new Date().toLocaleTimeString();
const timer = setInterval(() => {
time = new Date().toLocaleTimeString();
m.redraw();
}, 1000);
return {
view: () => m("p", `Current time: ${time}`),
onremove: () => clearInterval(timer),
};
}
Component composition
Props
Ember Polaris
import UserProfile from "./user-profile.gjs";
const favoriteColors = ["green", "blue", "red"];
<template>
<UserProfile
@name="John"
@age={{20}}
@favouriteColors={{favoriteColors}}
@isAvailable={{true}}
/>
</template>
Mithril
import m from "mithril";
import UserProfile from "./UserProfile.js";
export default function App() {
return {
view: () =>
m(UserProfile, {
name: "john",
age: 20,
favouriteColors: ["green", "blue", "red"],
isAvailable: true,
}),
};
}
Emit to parent
Ember Polaris
<template>
<button {{on "click" @onYes}}> YES </button>
<button {{on "click" @onNo}}> NO </button>
</template>
Mithril
import m from "mithril";
export const AnswerButton = ({ attrs: { onYes, onNo } }) => ({
view: () =>
m(
"div",
m("button", { onclick: onYes }, "YES"),
m("button", { onclick: onNo }, "NO"),
),
});
Slot
Ember Polaris
import FunnyButton from "./funny-button";
<template>
<FunnyButton>Click me!</FunnyButton>
</template>
Mithril
import m from "mithril";
import { FunnyButton } from "./FunnyButton.jsx";
export default function App() {
return {
view: () => m(FunnyButton, "Click me!"),
};
}
Slot fallback
Ember Polaris
import FunnyButton from "./funny-button";
<template>
<FunnyButton />
<FunnyButton>I got content!</FunnyButton>
</template>
Mithril
import m from "mithril";
import FunnyButton from "./FunnyButton.jsx";
export default function App() {
return {
view: () => m("", m(FunnyButton), m(FunnyButton, "I got Content")),
};
}
Context
Ember Polaris
import UserProfile from "./user-profile";
<template>
<UserProfile />
</template>
Mithril
import m from "mithril";
import UserProfile from "./UserProfile";
export default function App() {
const user = {
id: 1,
username: "unicorn42",
email: "[email protected]",
};
const updateUsername = (username) => (user.username = username);
return {
view: () =>
m(
"",
m("h1", `Welcome Back, ${user.username}`),
m(UserProfile, { user, updateUsername }),
),
};
}
Form input
Input text
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
export default class InputHello extends Component {
@tracked text = "Hello World";
handleInput = (event) => (this.text = event.target.value);
<template>
<p>{{this.text}}</p>
<input value={{this.text}} {{on "input" this.handleInput}} />
</template>
}
Mithril
import m from "mithril";
export default function InputHello() {
let text = "Hello world";
const handleChange = ({ target: { value } }) => (text = value);
return {
view: () =>
m("", m("p", text), m("input", { value: text, onchange: handleChange })),
};
}
Checkbox
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
export default class InputHello extends Component {
@tracked isAvailable = false;
handleChange = (event) => (this.isAvailable = event.target.checked);
<template>
<input
id="is-available"
type="checkbox"
checked={{this.isAvailable}}
{{on "change" this.handleChange}}
/>
<label for="is-available">Is available</label>
</template>
}
Mithril
import m from "mithril";
export default function IsAvailable() {
let isAvailable = false;
const onUpdate = () => (isAvailable = !isAvailable);
return {
view: () =>
m(
"",
m("input", {
id: "is-available",
type: "checkbox",
checked: isAvailable,
onchange: onUpdate,
}),
m("label", { for: "is-available" }, "Is available"),
),
};
}
Radio
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
export default class PickPill extends Component {
@tracked picked = "red";
handleChange = (event) => (this.picked = event.target.value);
<template>
<div>Picked: {{this.picked}}</div>
<input
id="blue-pill"
type="radio"
value="blue"
checked={{eq this.picked "blue"}}
{{on "change" this.handleChange}}
/>
<label htmlFor="blue-pill">Blue pill</label>
<input
id="red-pill"
type="radio"
value="red"
checked={{eq this.picked "red"}}
{{on "change" this.handleChange}}
/>
<label htmlFor="red-pill">Red pill</label>
</template>
}
Mithril
import m from "mithril";
export default function PickPill() {
let picked = "red";
let pills = ["red", "green", "blue"];
const handleChange = ({ target: { value } }) => (picked = value);
return {
view: () =>
m(
"",
m("", `Picked: ${picked}`),
pills.map((pill) =>
m(
".",
m("input", {
id: pill,
checked: picked == pill,
type: "radio",
value: pill,
onchange: handleChange,
}),
m("label", { for: pill }, pill),
),
),
),
};
}
Select
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
export default class ColorSelect extends Component {
@tracked selectedColorId = 2;
select = (event) => (this.selectedColorId = event.target.value);
isSelected = (colorId) => this.selectedColorId === colorId;
colors = [
{ id: 1, text: "red" },
{ id: 2, text: "blue" },
{ id: 3, text: "green" },
{ id: 4, text: "gray", isDisabled: true },
];
<template>
<select {{on "change" this.select}}>
{{#each this.colors as |color|}}
<option
value={{color.id}}
disabled={{color.isDisabled}}
selected={{this.isSelected color.id}}
>
{{color.text}}
</option>
{{/each}}
</select>
</template>
}
Mithril
import m from "mithril";
const colors = [
{ id: 1, text: "red" },
{ id: 2, text: "blue" },
{ id: 3, text: "green" },
{ id: 4, text: "gray", isDisabled: true },
];
export default function ColorSelect() {
let selectedColorId = 2;
const handleSelect = ({ target: { value } }) => (selectedColorId = value);
return {
view: () =>
m(
"select",
{ value: selectedColorId, onchange: handleSelect },
colors.map(({ id, text, isDisabled }) =>
m("option", { key: id, id, disabled: isDisabled, value: id }, text),
),
),
};
}
Webapp features
Render app
Ember Polaris
<!doctype html>
<html>
<body>
<script type="module" src="./index.js"></script>
</body>
</html>
Mithril
<!doctype html>
<html>
<body>
<div id="app"></div>
<script type="module" src="./main.jsx"></script>
</body>
</html>
Fetch data
Ember Polaris
import Component from "@glimmer/component";
import { tracked } from "@glimmer/tracking";
class State {
@tracked isLoading = false;
@tracked error = null;
@tracked data = null;
}
function fetchUsers() {
let state = new State();
async function fetchData() {
try {
let response = await fetch("https://randomuser.me/api/?results=3");
let { results: users } = await response.json();
state.data = users;
state.error = null;
} catch (err) {
state.data = null;
state.error = err;
}
state.isLoading = false;
}
fetchData();
return state;
}
export default class App extends Component {
<template>
{{#let (this.fetchUsers) as |request|}}
{{#if request.isLoading}}
<p>Fetching users...</p>
{{else if request.error}}
<p>An error occurred while fetching users</p>
{{else}}
<ul>
{{#each request.data as |user|}}
<li>
<img src={{user.picture.thumbnail}} alt="user" />
<p>{{user.name.first}} {{user.name.last}}</p>
</li>
{{/each}}
</ul>
{{/if}}
{{/let}}
</template>
}
Mithril
import m from "mithril";
export default function App() {
let isLoading = false;
let error = null;
let users = [];
async function fetchUsers() {
isLoading = true;
try {
const { results } = await m.request(
"https://randomuser.me/api/?results=3",
);
users = results;
} catch (err) {
error = err;
}
isLoading = false;
}
return {
oninit: fetchUsers,
view() {
if (isLoading) return m("p", "Fetching users...");
if (error) return m("p", "An error occurred while fetching users");
return users.map((user) =>
m(
"li",
{ key: user.login.uuid },
m("img", { src: user.picture.thumbnail, alt: "user" }),
m("p", `${user.name.first} ${user.name.last}`),
),
);
},
};
}