Object() 构造函数

¥Syntax

new Object()
new Object(value)

Object()
Object(value)

注意：Object() 可以与 new 一起调用，也可以不与 new 一起调用，但有时效果不同。参见 返回值。

¥Note: Object() can be called with or without new, but sometimes with different effects. See Return value.

¥Parameters

value Optional

任何值。

¥Return value

当 Object() 构造函数本身被调用或构造时，它的返回值是一个对象：

¥When the Object() constructor itself is called or constructed, its return value is an object:

• 如果值为 null 或 undefined，它将创建并返回一个空对象。
• 如果该值已经是一个对象，则返回该值。
• 否则，它返回与给定值对应的类型的对象。例如，传递 BigInt 原语将返回 BigInt 封装对象。

当 Object() 被构造但 new.target 不是 Object 构造函数本身时，行为略有不同 - 它初始化一个以 new.target.prototype 作为其原型的新对象。任何参数值都会被忽略。例如，当 Object() 在 延伸 Object 的类的构造函数中通过 super() 隐式调用时，可能会发生这种情况。在这种情况下，即使将数字传递给 super()，构造函数内的 this 值也不会成为 Number 实例。

¥When Object() is constructed but new.target is not the Object constructor itself, the behavior is slightly different — it initializes a new object with new.target.prototype as its prototype. Any argument value is ignored. This may happen, for example, when Object() is implicitly called via super() in the constructor of a class that extends Object. In this case, even if you pass a number to super(), the this value inside the constructor does not become a Number instance.

¥Examples

¥Creating a new Object

const o = new Object();
o.foo = 42;

console.log(o);
// { foo: 42 }

¥Using Object given undefined and null types

以下示例将空 Object 对象存储在 o 中：

¥The following examples store an empty Object object in o:

const o = new Object();

const o = new Object(undefined);

const o = new Object(null);

¥Obtaining wrapper objects for BigInt and Symbol

当使用 new 调用时，BigInt() 和 Symbol() 构造函数会抛出错误，以防止创建封装对象而不是原始值的常见错误。为这些类型创建封装对象的唯一方法是使用它们调用 Object()：

¥The BigInt() and Symbol() constructors throw an error when called with new, to prevent the common mistake of creating a wrapper object instead of the primitive value. The only way to create a wrapper object for these types is to call Object() with them:

const numberObj = new Number(1);
console.log(typeof numberObj); // "object"

const bigintObj = Object(1n);
console.log(typeof bigintObj); // "object"

const symbolObj = Object(Symbol("foo"));
console.log(typeof symbolObj); // "object"

¥See also

• 对象初始值设定项