什么是instance.constructor.constructor，它如何工作?

问题描述

function Person(name) {
    this.name = name;
}   

let person1 = new Person("Eve");

person1.constructor; // Output: ƒ Person(name) {}

person1.constructor.constructor; // Output: ƒ Function() { [native code] }

person1.constructor.constructor("console.log(1)"); // Output: ƒ anonymous() {console.log(1)}

person1.constructor.constructor("console.log(1)")(); // Output: 1

有人可以帮助我理解 person1.constructor.constructor ， person1.constructor.constructor("console.log(1)")和person1.constructor.constructor("console.log(1)")()?我不明白这些输出.

Can someone help me to understand person1.constructor.constructor, person1.constructor.constructor("console.log(1)") and person1.constructor.constructor("console.log(1)")()? I do not understand the outputs.

推荐答案

实例的 .constructor 属性指向与内部原型关联的函数.如您所见， person1.constructor 为您提供 Person ，因为 person1 是用 new Person ( person1 的内部原型是 Person.prototype )

The .constructor property of an instance points to the function associated with the internal prototype. As you can see, person1.constructor gives you Person, because person1 was created with new Person (person1's internal prototype is Person.prototype)

什么是 Person ?这是一个功能.函数的 .constructor 将是与该函数的内部原型相关联的函数-即与 Function.prototype 相关联的构造函数，即 Function，函数构造函数:

What is the Person? It's a function. The .constructor of a function will be the function associated with the internal prototype of that function - that is, the constructor associated with Function.prototype, which is Function, the function constructor:

function Person(name) {
    this.name = name;
}   

let person1 = new Person("Eve");

console.log(person1.constructor.constructor === Function);

您可以将字符串传递给 new Function 以从中创建函数.

You can pass strings to new Function to create functions out of them.

person1.constructor.constructor("console.log(1)");

就像

Function("console.log(1)");

返回一个函数，该函数在调用时将记录为1.

which returns a function that, when called, logs 1.

const fn = Function("console.log(1)");
console.log(fn);
fn();

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