It is corret usage to create a tab for mithril? - mithril.js

Question

I want to create a simple Tab but I think it is strange for my using:
var root = document.body
var index = {
view: () => index.html,
html: m('div', { id: 'div1' }, [
[
(function () {
let value = ["A", "B", "C", "D"]
let output = []
for (let i = 0; i < 4; i++) {
output.push(m('input', {
class: (function () {
if (i == 0) return "onit"
})(),
type: 'button',
value: value[i],
onclick: function () {
let div1 = document.getElementById("div1")
let btn = div1.getElementsByTagName("input")
let div1_div = div1.getElementsByTagName("div")
let _this = this
let num = (function () {
for (let i = 0; i < btn.length; i++) {
if (btn[i] == _this) {
return i
}
}
})()
for (let i = 0; i < btn.length; i++) {
btn[i].className = ""
}
this.className = "onit"
for (let i = 0; i < div1_div.length; i++) {
div1_div[i].setAttribute("style", "dispaly:none")
}
div1_div[num].setAttribute("style", "display:block")
}
}))
}
return output
})()
],
[
(function () {
let arr = ["aaa", "bbb", "ccc", "ddd"]
let output = []
for (let i = 0; i < 4; i++) {
output.push(m("div", { style: (the => i == 0 ? "display:block" : undefined)() }, arr[i]))
}
return output
})()
]
])
}
m.route(root, "/index", {
"/index": index
})
Is there any other simple way to achieve this?
If I click the button, the style of button will change and the display of all "div" will be changed. Screenshot

Answer 1

In mithril.js views you can only use expressions, for-loops, ifs and so on are no expressions and only possible the way you did it. Nevertheless there are other ways to achieve this
Loops can be achieved using the functional counterparts
let values = ["A", "B", "C", "D"]
let output = []
function(){
for (let i = 0; i < 4; i++) {
output.push(m('span', value)
}
return output
}()
can be written as
values.map(value => m('span', value)
if-Statements can be written using the ternary expression
function() {
if (condition) {
return 'this'
} else {
return 'that'
}
}()
just use
condition ? 'this' : 'that'
You can also use view functions if your view code gets to deeply nested and you need custom logic:
function someOtherView(someData) {
if (someData.shouldBeShown) {
return someData.text
}
}
function someView() {
...
someOtherView(someData)
...
}
This also makes your views more readable.