Javascript 过滤空对象属性

Question

我有一个包含一个或多个对象的数组，我想过滤掉所有空属性:

asset = [{"ObjId":177791,"ObjCreditlineM":"DEU","ObjReprorechtM":null,"ObjKommentarM":null,"ObjZustandM":null,"ObjReserve01M":null,"ObjReserve02M":null,"ObjFeld01M":null,"ObjFeld02M":null,"ObjFeld03M":null,"ObjFeld04M":"Foto","ObjFeld05M":null,"ObjFeld06M":null,"ObjFeld07M":null,"ObjFeld01S":null,"ObjFeld02S":null,"ObjFeld03S":null,"ObjFeld04S":null,"ObjFeld05S":null,"ObjFeld06S":null,"ObjFeld07S":null,"ObjFeld01F":0,"ObjFeld02F":0,"ObjFeld01D":null,"ObjFeld02D":null,"ObjInv01S":null,"ObjInv02S":null,"ObjInv03S":null,"ObjInv04S":null,"ObjInv05S":null,"ObjInv06S":null,"ObjDinId":0,"ObjReferenz01Id":null,"ObjReferenz02Id":null,"ObjTransferId":null,"ObjGesperrtS":null,"ObjIconTextM":null}]


// My attempt:

var filledProps = asset.map(el => { 
  if (Object.keys(el)) { // check if object property value is not null
    return el;
  };
});

console.log(filledProps);

但是我得到了相同的对象属性。我错过了什么？

Answer 1

听起来您想用新对象创建一个新数组，这些新对象只具有不属于 null 的属性。从原文。是这样，map是你想开始的地方，但是 Object.keys(el)总是真实的，因为它返回一个属性名称数组。你虽然很接近:

var asset = [{"ObjId":177791,"ObjCreditlineM":"DEU","ObjReprorechtM":null,"ObjKommentarM":null,"ObjZustandM":null,"ObjReserve01M":null,"ObjReserve02M":null,"ObjFeld01M":null,"ObjFeld02M":null,"ObjFeld03M":null,"ObjFeld04M":"Foto","ObjFeld05M":null,"ObjFeld06M":null,"ObjFeld07M":null,"ObjFeld01S":null,"ObjFeld02S":null,"ObjFeld03S":null,"ObjFeld04S":null,"ObjFeld05S":null,"ObjFeld06S":null,"ObjFeld07S":null,"ObjFeld01F":0,"ObjFeld02F":0,"ObjFeld01D":null,"ObjFeld02D":null,"ObjInv01S":null,"ObjInv02S":null,"ObjInv03S":null,"ObjInv04S":null,"ObjInv05S":null,"ObjInv06S":null,"ObjDinId":0,"ObjReferenz01Id":null,"ObjReferenz02Id":null,"ObjTransferId":null,"ObjGesperrtS":null,"ObjIconTextM":null}]

// Use `map` to get a new array with new objects
var filledProps = asset.map(el => {
  // Loop the property names of `el`, creating a new object
  // with the ones whose values aren't `null`.
  // `reduce` is commonly used for doing this:
  return Object.keys(el).reduce((newObj, key) => {
    const value = el[key];
    if (value !== null) {
      newObj[key] = value;
    }
    return newObj;
  }, {});
});
console.log(filledProps);

What am I missing?

从 if (Object.keys(el))总是真实的，你的代码总是返回 el不变。它不是创建新对象，也不是使用 null 删除属性原始对象的值。

以上创建了新对象，但如果您愿意，您可以从具有 null 的原始对象中删除属性。取而代之的是:

var asset = [{"ObjId":177791,"ObjCreditlineM":"DEU","ObjReprorechtM":null,"ObjKommentarM":null,"ObjZustandM":null,"ObjReserve01M":null,"ObjReserve02M":null,"ObjFeld01M":null,"ObjFeld02M":null,"ObjFeld03M":null,"ObjFeld04M":"Foto","ObjFeld05M":null,"ObjFeld06M":null,"ObjFeld07M":null,"ObjFeld01S":null,"ObjFeld02S":null,"ObjFeld03S":null,"ObjFeld04S":null,"ObjFeld05S":null,"ObjFeld06S":null,"ObjFeld07S":null,"ObjFeld01F":0,"ObjFeld02F":0,"ObjFeld01D":null,"ObjFeld02D":null,"ObjInv01S":null,"ObjInv02S":null,"ObjInv03S":null,"ObjInv04S":null,"ObjInv05S":null,"ObjInv06S":null,"ObjDinId":0,"ObjReferenz01Id":null,"ObjReferenz02Id":null,"ObjTransferId":null,"ObjGesperrtS":null,"ObjIconTextM":null}];

asset.forEach(el => {
  Object.keys(el).forEach(key => {
    if (el[key] === null) {
      delete el[key];
    }
  });
});
console.log(asset);

但是，有两个方面需要指出:

它修改了原始对象(因此，在某种程度上，原始数组)。

当您从对象中删除属性时，它可能会影响之后对该对象的属性查找性能。 99.999% 的时间你不在乎，但它就在那里。