One. prototype is secretly created only for constructor functions.
Even if you create a plain object, array, etc., there is no prototype.
That’s it.
So what if you want to inherit something like a plain object?
Either create a constructor function.. Or use Object.create(), as we will tell you next time, or class, or one of the three.
2. If you want to find the genes of your parents, you can print __proto__.
Child objects created from the parent have a property called __proto__.
If you print this out, the parent’s prototype will be printed out.
So __proto__ has the same meaning as the parent’s prototype.
Let’s print it out for real.
function machine() {
this.name = "Kim";
this.age = 15;
}
var student1 = new machine();
console.log(student1.__proto__);
console.log(machine.prototype);
student1.__proto__
machine.prototype
If you print out each one, does it come out the same?
Anyway, “__proto__ means the parent prototype“.
You can just think of __proto__ as such a value that can be used when you want to genetically test what your parent’s gene is.
3. If you register __proto__ directly, you can implement inheritance function between object.
__proto__ means prototype of parent.
So what if we forcibly set a __proto__ on some object?
Oh, there are parents like this.
It’s a kind of genetic engineering, let’s try it.
var parent = { name: "Kim" };
var child = {};
child.__proto__ = parent;
console.log(child.name);
Now we have created parent and child objects one by one.
And on the third line, we put the parent in the child’s __proto__.
Then, the parent gene of the child becomes an object named { name : 'Kim' }.
After that, the child is now free to use the child .name property.
You can also implement the inheritance function like this.
