你可以通過多種方法遍歷JavaScript對象的屬性或值，因為對象本身不可直接用for...of迭代，1. 使用for...in循環(huán)結(jié)合hasOwnProperty()可遍歷自身可枚舉屬性鍵；2. 使用Object.keys()配合for...of可迭代對象自身的鍵；3. 使用Object.values()配合for...of可獲取所有自身可枚舉屬性的值；4. 使用Object.entries()配合for...of或forEach()可同時獲取鍵值對；5. 使用Object.getOwnPropertyNames()可包含非枚舉屬性名，但不包括Symbol屬性，推薦根據(jù)需求選擇方法，並註意區(qū)分自身與繼承屬性。

You can't directly iterate over an object in JavaScript using standard loop constructs like for...of , because objects are not iterable by default. However, there are several ways to loop through an object's properties or values, depending on what you need.

Here are the most common and effective methods:

1. for...in loop (Iterate over keys)

The for...in loop goes through all enumerable string properties of an object, including inherited ones (from the prototype chain), so it's important to use hasOwnProperty() to filter out inherited properties.

 const obj = { a: 1, b: 2, c: 3 };

for (let key in obj) {
  if (obj.hasOwnProperty(key)) {
    console.log(key, obj[key]);
  }
}
// Output:
// a 1
// b 2
// c 3

This is the most traditional way and works in older environments.

2. Object.keys() for...of (Iterate over keys)

Object.keys() returns an array of an object's own enumerable property names (keys), which you can then iterate over.

 const obj = { a: 1, b: 2, c: 3 };

for (let key of Object.keys(obj)) {
  console.log(key, obj[key]);
}
// Output:
// a 1
// b 2
// c 3

This is clean and modern, and allows you to use array methods if needed.

3. Object.values() for...of (Iterate over values)

If you only care about the values, use Object.values() .

 const obj = { a: 1, b: 2, c: 3 };

for (let value of Object.values(obj)) {
  console.log(value);
}
// Output:
// 1
// 2
// 3

4. Object.entries() for...of (Iterate over key-value pairs)

Use Object.entries() to get an array of [key, value] pairs. This is especially useful when you need both key and value.

 const obj = { a: 1, b: 2, c: 3 };

for (let [key, value] of Object.entries(obj)) {
  console.log(key, value);
}
// Output:
// a 1
// b 2
// c 3

You can also use this with .forEach() :

 Object.entries(obj).forEach(([key, value]) => {
  console.log(key, value);
});

5. Using Object.getOwnPropertyNames()

Similar to Object.keys() , but includes non-enumerable properties (except symbols).

 for (let key of Object.getOwnPropertyNames(obj)) {
  console.log(key, obj[key]);
}

Useful if you need to include non-enumerable own properties.

Important Notes:

• Symbols : None of the above methods (except Object.getOwnPropertySymbols() ) include properties with symbol keys.
• Prototype properties : Always prefer hasOwnProperty() with for...in , or use Object.keys() / entries() which only include own properties.
• Order : Since ES2015, the order of properties is predictable: keys appear in the order they were added, for string keys that aren't integers.

In short, for most use cases:

• Use for...in with hasOwnProperty() for broad compatibility.
• Use Object.keys() , Object.values() , or Object.entries() with for...of or array methods for cleaner, modern code.

Basically, pick the method based on whether you need keys, values, or both — and whether you want only own properties.

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