Object

Prototype

• Get prototype
• __proto__
• Object.getPrototypeOf(obj)
• Set prototype
• Object.setPrototypeOf(obj, proto)

Create object

• {}
• new Object()
• Object.create(proto)
• constructor function
• class

Basic method

• Object.values(obj)
• Object.keys(obj)
• Object.entries(obj)
• Object.fromEntries(iterable)
• Object.hasOwn(obj, key)
• filter inherienced properties
• Object.getOwnPropertyNames(obj)
• return an array of all properties (including non-enumerable properties) found directly upon a given object.

判断 key 是否是原生的

Object.hasOwn(obj, key);

iterate object

for (const [key, value] of Object.entries(obj)) {
  console.log(key, value);
}
Object.entries(obj).map(([key, value]) => {
  console.log(key, value);
});

判断是否是 object

• typeof obj === 'object' && obj !== null
• 不能判断obj是Array，Function等。
• isPlainObject 判断是否是纯对象，排除Array，Function等。

function isPlainObject(value) {
  if (value == null) {
    return false;
  }

  const prototype = Object.getPrototypeOf(value);
  return prototype === null || prototype === Object.prototype;
}

Object.assign

• 浅拷贝
• 返回新对象
• 会跳过undefined和null
• 会跳过Symbol
• 会跳过getter和setter