为什么对于使用带参数的构造函数的单例实例，instanceof 返回 false？

发布于 2024-12-05 09:44:32 字数 545 浏览 1 评论 0原文

我正在尝试检查代码中是否存在特定类型的对象。即使对象的原型中有构造函数，它仍然无法返回正确的对象类型，并且在使用instanceof运算符时总是返回“object”。

这是该对象的示例：

Simple = (function(x, y, z) {
    var _w = 0.0;

    return {
        constructor: Simple,

        x: x || 0.0,
        y: y || 0.0,
        z: z || 0.0,

        Test: function () {
            this.x += 1.0;
            this.y += 1.0;
            this.z += 1.0;

            console.log("Private: " + _w);
            console.log("xyz: [" + this.x + ", " + this.y + ", " + this.z + "]");
        }
    }
});

原文

I'm trying to check for a specific type of object in my code. Even though the object has the constructor in its prototype, it is still failing to return the correct object type and always returns with "object" when using the instanceof operator.

Here's an example of the object:

Simple = (function(x, y, z) {
    var _w = 0.0;

    return {
        constructor: Simple,

        x: x || 0.0,
        y: y || 0.0,
        z: z || 0.0,

        Test: function () {
            this.x += 1.0;
            this.y += 1.0;
            this.z += 1.0;

            console.log("Private: " + _w);
            console.log("xyz: [" + this.x + ", " + this.y + ", " + this.z + "]");
        }
    }
});

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天煞孤星 2024-12-12 09:44:32

您将返回一个带有 constructor 属性的对象文字，以设置为函数 Simple。内部构造函数仍设置为 Object，因此 instanceof 返回 false。
要使 instanceof 返回 true，您需要在构造函数中使用 this.property 设置属性或使用原型，并使用 new Simple()< /代码>。

function Simple(x, y, z) {
    var _w = 0.0;

    this.x = x || 0.0;
    this.y = y || 0.0;
    this.z = z || 0.0;

    this.Test = function () {
            this.x += 1.0;
            this.y += 1.0;
            this.z += 1.0;

            console.log("Private: " + _w);
            console.log("xyz: [" + this.x + ", " + this.y + ", " + this.z + "]");
        }
  });
  (new Simple()) instanceof Simple //true

You're returning an object literal with the constructor property to set to the function Simple. The internal constructor is still set to Object, so instanceof returns false.
For instanceof to return true, you need to set properties using this.property in the constructor or use prototypes, and initalize a new object using new Simple().

function Simple(x, y, z) {
    var _w = 0.0;

    this.x = x || 0.0;
    this.y = y || 0.0;
    this.z = z || 0.0;

    this.Test = function () {
            this.x += 1.0;
            this.y += 1.0;
            this.z += 1.0;

            console.log("Private: " + _w);
            console.log("xyz: [" + this.x + ", " + this.y + ", " + this.z + "]");
        }
  });
  (new Simple()) instanceof Simple //true

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