为什么事件属性不容易获得? [英] Why event properties are not easy to get?

问题描述

我有以下代码( 这里 是可编辑的示例-用法:在输入字段中输入并观看控制台):

I have following code ( HERE is editable example - usage: type in input field and watch console):

function test(event) 
{	  
  let keys = Object.keys(event);
  let keysOwnProp = Object.getOwnPropertyNames(event);
  let keysForIn=[]; for(let k in event) { keysForIn.push(k); }


  console.log('keysForIn',keysForIn);
  console.log('keys',JSON.stringify(keys));
  console.log('keysOwnProp',JSON.stringify(keysOwnProp));
}

<input oninput="test(event)" placeholder="type something">

问题:

• 为什么仅在keysForIn中可以看到所有(?)事件字段/属性，但是在keys和keysOwnProp中却只有一个:isTrusted?
• keysForIn是否有替代方法(如果是，请提供)?

• Why only in keysForIn I see all(?) event fields/properties, but in keys and keysOwnProp only one: isTrusted?
• Is there an alternative for keysForIn (if yes, provide it) ?

推荐答案

在这里我复制粘贴GrégoryNEUT 答案-看起来是最好的答案:

Here I copy-paste Grégory NEUT answer - which looks like is the best one:

Object.keys(...)返回对象的非符号可枚举属性的名称，但仅返回未继承的属性的名称.

Object.keys(...) returns the names of the non-symbol enumerable properties of the object, but only the ones which are not inherited.

For...in迭代对象的非符号可枚举属性的名称，无论是否继承.

For...in iterates the names of the non-symbol enumerable properties of the object, inherited or not.

Object.getOwnPropertyNames(...)返回所有非符号属性(是否可枚举).

Object.getOwnPropertyNames(...) returns all non-symbol properties (enumerable or not).

据我所知，for ... in除了获得继承的属性外别无选择

To my knowledge there is no alternative to for ... in to get inherited properties

function displayDetail(o) {
  let keys = Object.keys(o);

  console.log('Object.keys > ', keys);

  let keysOwnProp = Object.getOwnPropertyNames(o);

  console.log('getOwnPropertyNames > ', keysOwnProp);

  const keysForIn = [];

  for (let k in o) {
    keysForIn.push(k);
  }

  console.log('for ... in > ', keysForIn);
}


/**
 * The basic object
 */
const obj = {
  own: 'A',
};

/**
 * We add a non enumerable property to the object
 */
Object.defineProperty(obj, 'notEnumerable', {
  enumerable: false,
  value: 123,
});

/**
 * We create a new object based on the first (it will inherit it's properties)
 */
const objWithInheritedProperties = Object.create(obj);

console.log('REGULAR OBJECT\n');
displayDetail(obj);

console.log('\n-----------\n');

console.log('OBJECT WITH INHERITANCE\n');
displayDetail(objWithInheritedProperties);

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