apply-properties.js

var isObject = require("is-object")
var isHook = require("vtree/is-vhook")

module.exports = applyProperties

function applyProperties(node, props, previous) {
    for (var propName in props) {
        var propValue = props[propName]

        if (propValue === undefined) {
            removeProperty(node, props, previous, propName);
        } else if (isHook(propValue)) {
            propValue.hook(node,
                propName,
                previous ? previous[propName] : undefined)
        } else {
            if (isObject(propValue)) {
                patchObject(node, props, previous, propName, propValue);
            } else if (propValue !== undefined) {
                node[propName] = propValue
            }
        }
    }
}

function removeProperty(node, props, previous, propName) {
    if (previous) {
        var previousValue = previous[propName]

        if (!isHook(previousValue)) {
            if (propName === "attributes") {
                for (var attrName in previousValue) {
                    node.removeAttribute(attrName)
                }
            } else if (propName === "style") {
                for (var i in previousValue) {
                    node.style[i] = ""
                }
            } else if (typeof previousValue === "string") {
                node[propName] = ""
            } else {
                node[propName] = null
            }
        }
    }
}

function patchObject(node, props, previous, propName, propValue) {
    var previousValue = previous ? previous[propName] : undefined

    // Set attributes
    if (propName === "attributes") {
        for (var attrName in propValue) {
            var attrValue = propValue[attrName]

            if (attrValue === undefined) {
                node.removeAttribute(attrName)
            } else {
                node.setAttribute(attrName, attrValue)
            }
        }

        return
    }

    if(previousValue && isObject(previousValue) &&
        getPrototype(previousValue) !== getPrototype(propValue)) {
        node[propName] = propValue
        return
    }

    if (!isObject(node[propName])) {
        node[propName] = {}
    }

    var replacer = propName === "style" ? "" : undefined

    for (var k in propValue) {
        var value = propValue[k]
        node[propName][k] = (value === undefined) ? replacer : value
    }
}

function getPrototype(value) {
    if (Object.getPrototypeOf) {
        return Object.getPrototypeOf(value)
    } else if (value.__proto__) {
        return value.__proto__
    } else if (value.constructor) {
        return value.constructor.prototype
    }
}