document.querySelector("#btn_alignl").addEventListener("click", () => { Align.call(this, 'left') })
document.querySelector("#btn_alignc").addEventListener("click", () => { Align.call(this, 'center') })
document.querySelector("#btn_alignr").addEventListener("click", () => { Align('right') })

js 代碼：

1、一個公共的Align方法，參數(shù)為：left|center|right

/**
     * 1 通過getBoundaryEndNodes獲取所有末梢元素
     * 2 遍歷末梢節(jié)點,通過getBlockParent獲取每一個末梢節(jié)點的父級block元素
     * 3 設(shè)置endnode 的 blockparent.style.textAlign=left|center|right
     * @param alignStr left|center|right
     **/
    function Align(alignStr) {
        const rng = document.getSelection().getRangeAt(0)
        const commonAncestor = rng.commonAncestorContainer
        //獲取開始節(jié)點，到結(jié)尾節(jié)點之間的所有末梢節(jié)點
        let getBoundaryEndNodes = function (pNode) {
            if (pNode == boundaries.start) { boundaries.isStart = true }
            if (pNode == boundaries.end) {
                boundaries.isEnd = true
                resultNodes.push(pNode)
                console.log(pNode)
            }
            if (boundaries.isStart == true && boundaries.isEnd == false && pNode.hasChildNodes() == false) { resultNodes.push(pNode); console.log(pNode) }

            if (pNode.hasChildNodes() && boundaries.isEnd == false) {
                pNode.childNodes.forEach(node => {
                    getBoundaryEndNodes(node)
                });
            }
        }
        //獲取所有末梢節(jié)點
        let getEndNodes = function (node, nodes=[]) {
            if (node.hasChildNodes()) {
                node.childNodes.forEach(node => {
                    getEndNodes(node, nodes)
                });
            } else {
                nodes.push(node)
            }
            return nodes
        }

        const startBoundaryNode = getEndNodes(rng.startContainer)[0]
        const endBoundaryNode = getEndNodes(rng.endContainer).pop()
        let resultNodes = [] //存放開始節(jié)點，到結(jié)尾節(jié)點之間的所有末梢節(jié)點
        let boundaries = { start: startBoundaryNode, end: endBoundaryNode, isStart: false, isEnd: false }
        getBoundaryEndNodes.call(this, commonAncestor)
        //遍歷所有末梢節(jié)點，找到其塊父元素 設(shè)置對齊樣式
        resultNodes.forEach(node => {
            const blockparent = getBlockParent(node)
            if (!!blockparent && blockparent.style.textAlign != alignStr) {
                blockparent.style.textAlign = alignStr
            }
        })
    }

getBlockParent的實現(xiàn)--獲取選中末梢節(jié)點的塊父節(jié)點的實現(xiàn)

	let blockTags = ['p', 'h1', 'h2', 'h3', 'h4', 'h5', 'ul', 'ol', 'li', 'div', 'body', 'td', 'th']
    // let inlineTags = ['img', 'font', 'b', 'strong', 'span', 'a']
    let blockTagSet = new Map()
    blockTags.forEach((v) => { blockTagSet.set(v, true) });
    const source = document.querySelector('div.source');

    function getBlockParent(ele) {
        let result = undefined
        if (ele === source) {
            console.log('已找到editor的根，并沒有找父級block元素');
            result = undefined
        } else {
            switch (ele.nodeType) {
                //element: 判斷ele是否是塊級元素，判斷依據(jù)1 display:block 2 默認(rèn)的塊級元素
                case 1: {
                    const disPro = ele.style.display;
                    if (disPro && disPro.toLowerCase().indexOf('block') > -1) {
                        result = ele;
                    } else if (blockTagSet.get(ele.tagName.toLowerCase())) { result = ele }
                    else { result = getBlockParent(ele.parentElement) }
                    break;
                }
                case 3: {//textNode
                    if (!!ele.nodeValue.trim())
                        result = getBlockParent(ele.parentElement)
                    else result = undefined
                    break;
                }
                default: {
                    break;
                }
            } //end switch
        }//end if
        return result
    }