帮助我们高效操作的Virtual DOM简单实现

export default class VNode {
    constructor (tag, nodeType,key, props, text, children){
        this.tag = tag //element类型
        this.nodeType = nodeType //node类型，1为普通节点，3为文本节点，8为注释
        this.key = key
        this.props = props //node的属性
        this.text = text //文本节点的内容
        this.children = children//子节点
    }
    //将vnode渲染成DOM节点的方法
    render(){
        var el
        if(this.nodeType===1){
            el = document.createElement(this.tag)
            for(let prop in this.props){
                setAttr(el,prop,this.props[prop])
            }
            if(this.children){
                this.children.forEach(function(ch,i){
                    el.appendChild(ch.render())
                })
            }
        } else if(this.nodeType===3){
            el = document.createTextNode(this.text)
        } else if(this.nodeType===8){
            el = document.createComment(this.text)
        }
        el.key = this.key
        return el
    }
}
function setAttr(node,key,value){
    if(key==='style'){
        for(let val in value){
            node.style[val] = value[val]
        }
    } else {
        node.setAttribute(key,value)
    }
}

export default function diff(oldVNode, newVNode){
    directives = {}
    diffVNode(oldVNode,newVNode,directives)
    return directives
}

function diffVNode(oldVNode,newVNode){
    if(newVNode && isSameTypeNode(oldVNode,newVNode)){
        if(newVNode.nodeType===3 || newVNode.nodeType===8){
            if(oldVNode.text !== newVNode.text){
                addDirectives(newVNode.key,{type:TEXT, content: newVNode.text})
            }
        } else if(newVNode.nodeType===1){
            if(oldVNode.tag === newVNode.tag && oldVNode.key == newVNode.key){
                var propPatches = diffProps(oldVNode.props, newVNode.props)
                if(Object.keys(propPatches).length>0){
                    addDirectives(newVNode.key,{type:PROP, content: propPatches})
                }
                if(oldVNode.children || newVNode.children)
                    diffChildren(oldVNode.children,newVNode.children,newVNode.key)
            }
        }
    }
    return directives
}

function diffProps(oldProps,newProps){
    let patches={}
    if(oldProps){
        Object.keys(oldProps).forEach((prop)=>{
            if(prop === 'style' && newProps[prop]){
                let newStyle = newProps[prop]
                let isSame = true
                Object.keys(oldProps[prop]).forEach((item)=>{
                    if(prop[item] !== newStyle[item]){
                        isSame = false
                    }
                })
                if(isSame){
                    Object.keys(newStyle).forEach((item)=>{
                        if(!prop.hasOwnProperty(item)){
                            isSame = false
                        }
                    })
                }
                if(!isSame)
                    patches[prop] = newProps[prop]
            }
            if(newProps[prop] !== oldProps[prop]){
                patches[prop] = newProps[prop]
            }
        })
    }
    if(newProps){
       Object.keys(newProps).forEach((prop)=>{
        if(!oldProps.hasOwnProperty(prop)){
            patches[prop] = newProps[prop]
        }
    })
   }
    return patches
}

function diffChildren(oldChildren,newChildren,parentKey){
    oldChildren = oldChildren || []
    newChildren = newChildren || []
    let movedItem = []
    let oldKeyIndexObject = parseNodeList(oldChildren)
    let newKeyIndexObject = parseNodeList(newChildren)
    for(let key in newKeyIndexObject){
        if(!oldKeyIndexObject.hasOwnProperty(key)){
            addDirectives(parentKey,{type:INSERT,index:newKeyIndexObject[key],node:newChildren[newKeyIndexObject[key]]})
        }
    }
    for(let key in oldKeyIndexObject){
        if(newKeyIndexObject.hasOwnProperty(key)){
            if(oldKeyIndexObject[key] !== newKeyIndexObject[key]){
                let moveObj = {'oldIndex':oldKeyIndexObject[key],'newIndex':newKeyIndexObject[key]}
                movedItem[newKeyIndexObject[key]] = oldKeyIndexObject[key]
            }
            diffVNode(oldChildren[oldKeyIndexObject[key]],newChildren[newKeyIndexObject[key]])
        } else {
            addDirectives(key,{type:REMOVE,index:oldKeyIndexObject[key]})
        }
    }
    if(movedItem.length>0){
        addDirectives(parentKey,{type:MOVE, moved:movedItem})
    }
}

export default function patch(node,directives){
    if(node){
        var orderList = []
        for(let child of node.childNodes){
            patch(child,directives)
        }
        if(directives[node.key]){
            applyPatch(node,directives[node.key])
        }
    }
}

function applyPatch(node, directives){
    for(let directive of directives){
        switch (directive.type){
            case TEXT:
                setContent(node,directive.content)
                break
            case PROP:
                setProps(node,directive.content)
                break
            case REMOVE:
                removeNode(node)
                break
            case INSERT:
                insertNode(node,directive.node,directive.index)
            default:
                break
        }
    }
}