thunk.js

var createElement = require("virtual-dom/render")
var diff = require("virtual-dom/diff")
var patch = require("virtual-dom/patch")

module.exports = partial

function partial(fn) {
    var args = [].slice.call(arguments)

    return new Thunk(fn, args)
}

function Thunk(fn, args) {
    this.fn = fn
    this.args = args
    this.vnode = null
}

Thunk.prototype.type = "immutable-thunk"
Thunk.prototype.update = update
Thunk.prototype.init = init

function shouldUpdate(current, previous) {
    return current.fn === previous.fn &&
        current.args.every(function (arg, index) {
            return arg === previous[index]
        })
}

function update(previous, domNode) {
    if (!shouldUpdate(this, previous)) {
        this.vnode = previous.vnode
        return
    }

    this.vnode = (this.vnode || this.fn.apply(null, this.args))
    patch(domNode, diff(previous.vnode, this.vnode))
}

function init() {
    this.vnode = this.fn.apply(null, this.args)
    return createElement(this.vnode)
}