如何对事件对象进行字符串化？

Question

JSON.stringify(eventObject);

给予：

TypeError: Converting circular structure to JSON

---

dojox.json.ref.toJson(eventObject);

给予：

TypeError: Accessing selectionEnd on an input element that cannot have a selection.

---

是否有一些库/代码可以用来完成它？

Answer 1

您将无法使用 JSON.stringify 序列化事件对象，因为事件对象包含对 DOM 节点的引用，并且 DOM 到处都有循环引用（例如，子/父关系）。默认情况下 JSON 无法处理这些，所以你有点不走运。

我建议查看How to serialize DOM node to JSON even if there are circular references?，它对如何序列化 DOM 节点有一些建议。此外，以下问题似乎提供了有用的信息：

• How to save an object with circular references?
• Stringify (convert to JSON) a JavaScript object with circular reference

能够处理循环引用的 JSON 库似乎是

• JSON-js (see cycle.js)
• dojox.json.ref

或者，如果你不需要它们，你可以删除所有对 DOM 节点的引用，然后序列化对象。 毕竟你不应该这样做。见@PointedEars 评论:)

Answer 2

使用“替换器”功能避免错误：

JSON.stringify(evt, function(k, v) {
    if (v instanceof Node) {
        return 'Node';
    }
    if (v instanceof Window) {
        return 'Window';
    }
    return v;
}, ' ');

2019 年更新：浏览器 API 发生了一些变化，这是一种公开事件原型链中所有可用键的方法

function stringifyEvent(e) {
  const obj = {};
  for (let k in e) {
    obj[k] = e[k];
  }
  return JSON.stringify(obj, (k, v) => {
    if (v instanceof Node) return 'Node';
    if (v instanceof Window) return 'Window';
    return v;
  }, ' ');
}

Answer 3

我遇到了类似的问题，并编写了一个简单的事件序列化程序，其中包含一个帮助方法来清理事件的路径属性。此解决方案将数据从事件转换为可序列化对象的方法：

• 复制原始属性
• 为事件对象中的元素属性复制outerHTML
• 计算path属性的选择器路径（这样可以避免复制整个HTML页面的outerHTML）

// Calculate a string representation of a node's DOM path.
var pathToSelector = function(node) {
  if (!node || !node.outerHTML) {
    return null;
  }

  var path;
  while (node.parentElement) {
    var name = node.localName;
    if (!name) break;
    name = name.toLowerCase();
    var parent = node.parentElement;

    var domSiblings = [];

    if (parent.children && parent.children.length > 0) {
      for (var i = 0; i < parent.children.length; i++) {
        var sibling = parent.children[i];
        if (sibling.localName && sibling.localName.toLowerCase) {
          if (sibling.localName.toLowerCase() === name) {
            domSiblings.push(sibling);
          }
        }
      }
    }

    if (domSiblings.length > 1) {
      name += ':eq(' + domSiblings.indexOf(node) + ')';
    }
    path = name + (path ? '>' + path : '');
    node = parent;
  }

  return path;
};

// Generate a JSON version of the event.
var serializeEvent = function(e) {
  if (e) {
    var o = {
      eventName: e.toString(),
      altKey: e.altKey,
      bubbles: e.bubbles,
      button: e.button,
      buttons: e.buttons,
      cancelBubble: e.cancelBubble,
      cancelable: e.cancelable,
      clientX: e.clientX,
      clientY: e.clientY,
      composed: e.composed,
      ctrlKey: e.ctrlKey,
      currentTarget: e.currentTarget ? e.currentTarget.outerHTML : null,
      defaultPrevented: e.defaultPrevented,
      detail: e.detail,
      eventPhase: e.eventPhase,
      fromElement: e.fromElement ? e.fromElement.outerHTML : null,
      isTrusted: e.isTrusted,
      layerX: e.layerX,
      layerY: e.layerY,
      metaKey: e.metaKey,
      movementX: e.movementX,
      movementY: e.movementY,
      offsetX: e.offsetX,
      offsetY: e.offsetY,
      pageX: e.pageX,
      pageY: e.pageY,
      path: pathToSelector(e.path && e.path.length ? e.path[0] : null),
      relatedTarget: e.relatedTarget ? e.relatedTarget.outerHTML : null,
      returnValue: e.returnValue,
      screenX: e.screenX,
      screenY: e.screenY,
      shiftKey: e.shiftKey,
      sourceCapabilities: e.sourceCapabilities ? e.sourceCapabilities.toString() : null,
      target: e.target ? e.target.outerHTML : null,
      timeStamp: e.timeStamp,
      toElement: e.toElement ? e.toElement.outerHTML : null,
      type: e.type,
      view: e.view ? e.view.toString() : null,
      which: e.which,
      x: e.x,
      y: e.y
    };

    console.log(JSON.stringify(o, null, 2));
  }
};

// Create a mock event for this example
var evt = new MouseEvent("click", {
  bubbles: true,
  cancelable: true,
  view: window
});
var cb = document.getElementById("clicker");

// Add a click listener
cb.addEventListener("click", serializeEvent);

// Fire the event
cb.dispatchEvent(evt);

<div>
  <button id="clicker" /> JSONify my click!
</div>

Answer 4

Alexander Shutau 给出的代码的改进版本，因为它处理多级对象 (ES6)：

function stringify_object(object, depth=0, max_depth=2) {
    // change max_depth to see more levels, for a touch event, 2 is good
    if (depth > max_depth)
        return 'Object';

    const obj = {};
    for (let key in object) {
        let value = object[key];
        if (value instanceof Node)
            // specify which properties you want to see from the node
            value = {id: value.id};
        else if (value instanceof Window)
            value = 'Window';
        else if (value instanceof Object)
            value = stringify_object(value, depth+1, max_depth);

        obj[key] = value;
    }

    return depth? obj: JSON.stringify(obj);
}

只要这样称呼它：

stringify_object(event, 2);

例如，在一个 touchstart 事件中，我得到这个：

touchstart : {"isTrusted":true,"touches":{"0":{"identifier":0,"target":{"id":"screen"},"screenX":548,"screenY":281.5,"clientX":498.1817932128906,"clientY":185.90908813476562,"pageX":498.1817932128906,"pageY":185.90908813476562,"radiusX":29.77272605895996,"radiusY":27.954544067382812,"rotationAngle":0,"force":0.5},"length":1,"item":{}},"targetTouches":{"0":{"identifier":0,"target":{"id":"screen"},"screenX":548,"screenY":281.5,"clientX":498.1817932128906,"clientY":185.90908813476562,"pageX":498.1817932128906,"pageY":185.90908813476562,"radiusX":29.77272605895996,"radiusY":27.954544067382812,"rotationAngle":0,"force":0.5},"length":1,"item":{}},"changedTouches":{"0":{"identifier":0,"target":{"id":"screen"},"screenX":548,"screenY":281.5,"clientX":498.1817932128906,"clientY":185.90908813476562,"pageX":498.1817932128906,"pageY":185.90908813476562,"radiusX":29.77272605895996,"radiusY":27.954544067382812,"rotationAngle":0,"force":0.5},"length":1,"item":{}},"altKey":false,"metaKey":false,"ctrlKey":false,"shiftKey":false,"view":"Window","detail":0,"sourceCapabilities":{"firesTouchEvents":true},"which":0,"initUIEvent":{},"NONE":0,"CAPTURING_PHASE":1,"AT_TARGET":2,"BUBBLING_PHASE":3,"type":"touchstart","target":{"id":"screen"},"currentTarget":{"id":"screen"},"eventPhase":2,"bubbles":true,"cancelable":true,"defaultPrevented":false,"composed":true,"timeStamp":192516.7899999651,"srcElement":{"id":"screen"},"returnValue":true,"cancelBubble":false,"path":{"0":{"id":"screen"},"1":{"id":"back"},"2":{"id":""},"3":{"id":""},"4":{},"5":"Window"},"composedPath":{},"stopPropagation":{},"stopImmediatePropagation":{},"preventDefault":{},"initEvent":{}}

Answer 5

不确定它是否有帮助，但我只是在 Angular JS 文档中偶然发现了这一点：

*来源：https://code.angularjs.org/1.5.5/docs/guide/expression#-event-

/*
 * return a copy of an object with only non-object keys
 * we need this to avoid circular references
 */
function simpleKeys (original) {
  return Object.keys(original).reduce(function (obj, key) {
    obj[key] = typeof original[key] === 'object' ? '{ ... }' : original[key];
    return obj;
  }, {});
}

现在您可以执行以下操作：

JSON.stringify(simpleKeys(eventObject));

Answer 6

因此，问题在于 JSON.stringify 似乎在找到循环引用后立即退出。反正我对循环引用的属性不感兴趣。我得到其余的方法是

var str = "{"
for (var key in data) {
  if (JSON.stringify(data[key]) !== "") {
    str += key + ":" + data[key]) + ",";
  }
}
str += "}"

这基本上会给你剩下的属性。为避免 JS 错误，您可以将 if 放入 try/catch。

Answer 7

只需使用 JSON.stringify(event) 即可，事件数据应转换为字符串。