Why does newtoy.constructor === Gadget result in console false?
怪我咯
怪我咯 2017-06-26 10:57:07
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function Gadget(name,color){
    this.name=name;
    this.color=color;
    this.whatAreYou=function(){
        return 'I am a ' + this.color + ' ' + this.name;
    };
}

Gadget.prototype={
    price:100,
    rating:3,
    getInfo:function(){
        return 'Rating: ' + this.rating + ', price: ' + this.price;
    }
};

var newtoy=new Gadget('webcam','black');
new.rating;//3
newtoy.constructor === Gadget;//true

The above example is taken from the book "Object-Oriented Programming Guide"

怪我咯
怪我咯

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学霸

If the code is written correctly, it is false, because you have rewritten the prototype object of Gadget, and the prototype object you rewritten does not have a constructor attribute. You can refer to Chapter 6 of "JavaScript Advanced Programming" Introduction to prototype

typecho

The correct answer upstairs, Gadget.prototype has been rewritten. Because there is an implicit constructor in the prototype object, which points to the constructor itself. As follows:

Prototype expansion is best written in this form:

Test.prototype.newFn = function() {
    ...
}

Or use Object.assign() to merge objects:

Test.prototype = Object.assign(Test.prototype, {
    newAttr: '',
    newFn: function() {
        ...
    }
})
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