如何通过递归方法实现用json-diff渲染json字符串对比结果

前言

上一篇,对比了js-diff和json-diff,发现js-diff对比的结果返回的是拆分后字符串并且字符串中带有换行符跟空格,将拆分后的字符串拼接可以得到完整的两个json格式化后的信息。但是json-diff只返回了两个json中有修改的的部分,并且返回类型还要根据值类型来进行判断。

分析json-diff的结构

用两个数组嵌套对象,对象嵌套数组的比较复杂的json进行对比,获得的数据如下:

var json1 = {
  name: "小明",
  age: "22",
  hobby: ["篮球", "足球", "羽毛球"],
  grade: {
    English: ["130", "129", "135"],
    Chinese: ["120", "118", "122"],
    sports: ["90", "90", "90"],
  },
  honor: [{ desc: "获得数学竞赛第一名", info: [{ score: "100", ranking: 1 }, 2, 3] }],
}
var json2 = {
  name: "小红",
  age: "22",
  hobby: ["乒乓球", "羽毛球"],
  grade: {
    English: ["120", "129", "125"],
    Chinese: ["140", "139", "136"],
    sports: ["90", "90", "90"],
  },
  honor: [{ desc: "获得作文比赛第一名", info: [{ score: "99", rank: 2 }, 2, 3] }],
}
var jsonDiff = {
    "name": {
        "__old": "小明",
        "__new": "小红"
    },
    "hobby": [
        [
            "-",
            "篮球"
        ],
        [
            "-",
            "足球"
        ],
        [
            "+",
            "乒乓球"
        ],
        [
            " "
        ]
    ],
    "grade": {
        "English": [
            [
                "-",
                "130"
            ],
            [
                "+",
                "120"
            ],
            [
                " "
            ],
            [
                "-",
                "135"
            ],
            [
                "+",
                "125"
            ]
        ],
        "Chinese": [
            [
                "-",
                "120"
            ],
            [
                "-",
                "118"
            ],
            [
                "-",
                "122"
            ],
            [
                "+",
                "140"
            ],
            [
                "+",
                "139"
            ],
            [
                "+",
                "136"
            ]
        ]
    },
    "honor": [
        [
            "~",
            {
                "desc": {
                    "__old": "获得数学竞赛第一名",
                    "__new": "获得作文比赛第一名"
                },
                "info": [
                    [
                        "~",
                        {
                            "ranking__deleted": 1,
                            "rank__added": 2,
                            "score": {
                                "__old": "100",
                                "__new": "99"
                            }
                        }
                    ],
                    [
                        " "
                    ],
                    [
                        " "
                    ]
                ]
            }
        ]
    ]
};

可以观察到:

  • 字符串返回{"__old":string,"__new":string},数组返回[string[,string][,object]],非数组对象返回{ "key__added": string|object, "key__deleted": string|object, "key": string|object }。
  • 字符串通过__old、__new获取
  • 非数组对象新增属性从key__added获取,删除属性从key__deleted获取
  • 数组第一个值有四种类型空格表示未修改、+表示新增、-表示删除、~表示修改

解析结构图如下:

太绕了,画图之后才看的明白一点ORZ...

用递归方法拼接json字符串

首先创建一个函数用来判断json是否为数组,renderobj(diffObj, originObj, n),diffObj表示当层的diff对象,originObj表示当层的json1对象,n表示深度,第一层深度为0,主要为了方便计算缩进。

renderobj函数:

// 定义remove和add队列
const removeList = [];
const addlist = [];
if (diffObj instanceof Array) {
    // 数组的判断
} else if (typeof diffObj == "object"){
    if (diffObj.__new) {
        // 字符串修改
    } else {
        // 非数组对象修改
    }
}

字符串修改

当diffObj.__new为真时,__old同时有值,表示字符串做修改,此时可以直接把__new放到addList,__old存入removeList。

addlist.push(`<span style="color:red;">"${diffObj.__new}"</span>,<br/>`);
removeList.push(`<span style="color:red;">"${diffObj.__old}"</span>,<br/>`);

非数组对象修改

const { addHtml, removeHtml } = renderObject(diffObj, originObj, n);
addlist.push(addHtml);
removeList.push(removeHtml);

非数组对象要判断key的值,创建函数renderObject(diffObj, originObj, n),传参同renderobj。

const addlist = [];
const removeList = [];
addlist.push(`{</br>`);
removeList.push(`{</br>`);

// 遍历originObj,遍历diffObj...

addlist.push(`${spaceStr.repeat(n)}},</br>`);
removeList.push(`${spaceStr.repeat(n)}},</br>`);
return {
  addHtml: addlist.join(""),
  removeHtml: removeList.join(""),
};

为啥要分别遍历originObj和diffObj?因为json1对象中没有新增的key,diffObj中没有返回未修改key。

const spaceStr = "    ";
Object.keys(originObj).forEach(key => {
  const keyVal = diffObj[key];
  if (keyVal) {
   // renderobj重新判断修改类型
    const { addHtml, removeHtml } = renderobj(keyVal, originObj[key], n + 1);
    if (keyVal.__new) {
      // 当字符串修改时,将整行标红
      addlist.push("<div class="error-line-add">");
      removeList.push("<div class="error-line-remove">");
    }
    addlist.push(`${spaceStr.repeat(n + 1)}"${key}": ${addHtml}`);
    removeList.push(`${spaceStr.repeat(n + 1)}"${key}": ${removeHtml}`);
    if (keyVal.__new) {
      addlist.push(`</div>`);
      removeList.push(`</div>`);
    }
  } else {
    const remove = diffObj[key + "__deleted"];
    if (remove) {
      // 删除的属性
      removeList.push("<div class="error-line-remove">");
      removeList.push(
        `<span style="color:red;">${spaceStr.repeat(n + 1)}"${key}": ${renderJson(
          remove,
          n + 1
        )}</span></br>`
      );
      removeList.push("</div>");
    } else {
      // 没修改的属性直接存入
      addlist.push(
        `${spaceStr.repeat(n + 1)}"${key}": ${renderJson(originObj[key], n + 1)}</br>`
      );
      removeList.push(
        `${spaceStr.repeat(n + 1)}"${key}": ${renderJson(originObj[key], n + 1)}</br>`
      );
    }
  }
})
Object.keys(diffObj).forEach(key => {
  // 新增的属性,json1中没有,从diffObj中遍历
  if (key.includes("__added")) {
    addlist.push("<div class="error-line-add">");
    addlist.push(
      `<span style="color: red;">${spaceStr.repeat(n + 1)}"${key.replace("__added", "")}": "${diffObj[key]}",</br></span>`
    );
    addlist.push("</div>");
  }
});

数组对象修改

遍历diffObj,判断item[0]的值,当值为空格时,需要从json1中获取原属性值,diffObj中空格所在的索引位置有可能和originObj中索引的位置不同,要排除掉'+'新增的成员;当值为'+'时,直接将值存入addList;当值为'-'时,直接将值存入removeList;当值为'~'时,表示有修改,修改类型不确定需要重新循环判断。

addlist.push(`[</br>`);
removeList.push(`[</br>`);
diffObj.forEach((item, i) => {
    switch (item[0]) {
      case "~": {
        // 有修改,重新判断修改的值的类型
        const { addHtml, removeHtml } = renderobj(item[1], originObj[i], n + 1);
        addlist.push(`${spaceStr.repeat(n + 1)}${addHtml}`);
        removeList.push(`${spaceStr.repeat(n + 1)}${removeHtml}`);
        break;
      }
      case "-": {
        // 删除属性
        removeList.push("<div class="error-line-remove">");
        removeList.push(
          `<span style="color: red;">${spaceStr.repeat(n + 1)}${renderJson(
            item[1],
            n + 1
          )}</br>`
        );
        removeList.push("</div>");
        break;
      }
      case "+": {
        // 新增属性
        addlist.push("<div class="error-line-add">");
        addlist.push(
          `<span style="color: red;">${spaceStr.repeat(n + 1)}${renderJson(
            item[1],
            n + 1
          )}</br>`
        );
        addlist.push("</div>");
        break;
      }
      case " ": {
        // 属性未修改,从originObj中获取,注意对应的index不包括新增的属性
        const index = diffObj.slice(0, i).filter(item => item[0] != "+").length;
        const value = originObj[index];
        const itemStr = `${spaceStr.repeat(n + 1)}${renderJson(value, n + 1)}</br>`;
        addlist.push(itemStr);
        removeList.push(itemStr);
        break;
      }
    }
});
addlist.push(`${spaceStr.repeat(n)}],</br>`);
removeList.push(`${spaceStr.repeat(n)}],</br>`);

renderJson函数,用来格式化json值:

const renderJson = (json, n) => {
  if (!json) {
    return "";
  }
  if (typeof json == "string" || typeof json == "number") {
    return `"${json}",`;
  }
  return `${JSON.stringify(json, null, "	")
    .replace(new RegExp("
", "g"), `</br>${spaceStr.repeat(n)}`)
    .replace(new RegExp("	", "g"), spaceStr.repeat(n))},`;
};

最后对比显示结果如下:

总结

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原文地址:https://juejin.cn/post/7173554882526314532