如何字符串化事件对象？

时间：2012-07-18 18:08:31

标签： javascript json serialization stringify

JSON.stringify(eventObject);

给出：

TypeError: Converting circular structure to JSON

dojox.json.ref.toJson(eventObject);

给出：

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？

7 个答案:

答案 0 :(得分：16)

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在整个地方都有循环引用（例如子/父关系）。默认情况下，JSON无法处理这些问题，所以你在运气方面有点不幸。

我建议查看How to serialize DOM node to JSON even if there are circular references?，其中有一些关于如何序列化DOM节点的建议。此外，以下问题似乎也提供了有用的信息：

能够处理循环引用的JSON库似乎是

或者，如果不需要，可以删除对DOM节点的所有引用，然后序列化对象。毕竟不应该这样做。请参阅@PointedEars评论：）

答案 1 :(得分：7)

使用“replacer”功能来避免错误：

{{1}}

答案 2 :(得分：3)

不确定它是否有帮助，但我在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;
  }, {});
}

现在你可以这样做：

JSON.stringify(simpleKeys(eventObject));

答案 3 :(得分：1)

我遇到了类似的问题，并使用帮助器方法编写了一个简单的事件序列化程序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
  • 计算路径属性的选择器路径（这可以避免复制整个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>

答案 4 :(得分：0)

Alexander Shutau给出的代码的改进版本，因为它可以处理多层对象（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);
}

只需这样命名：

stringify_object(event, 2);

例如，在touchstart事件中，我得到了这个信息：

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":{}}

答案 5 :(得分：-1)

所以，问题是JSON.stringify一旦找到循环引用似乎就会纾困。无论如何，我对循环引用的属性不感兴趣。我得到其余部分的方式是

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

这基本上会为您提供其余的属性。为了避免JS错误，你可以将if放在try / catch中。

答案 6 :(得分：-1)

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

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