问题 如何在原型继承中创建新对象时覆盖函数？ [关闭]

var human = {
    name: '',
    gender: '',
    planetOfBirth: 'Earth',
    sayGender: function () {
        console.log(this.name + ' says my gender is ' + this.gender);
    },
    sayPlanet: function () {
        console.log(this.name + ' was born on ' + this.planetOfBirth);
    }
};

var male = Object.create(human, {
    gender: {value: 'Male'}
});

var female = Object.create(human, {
    gender: {value: 'Female'}
});


var david = Object.create(male, {
    name: {value: 'David'},
    planetOfBirth: {value: 'Mars', configurable: true}
});

var jane = Object.create(female, {
    name: {value: 'Jane'},
    sayPlanet: {value: function(){
        console.log("something different");
        }, writable: true, enumerable: true, configurable: true
    }
});

var Male = function(name){ // in this case the real constructor is female or male. Name is the only property that 'needs' to be initialized
    this.name = name;
    this.planetOfBirth = 'Jupiter';
}

Male.prototype = Object.create(male);

var john = new Male('John')

david.sayGender(); // David says my gender is Male
david.sayPlanet(); // David was born on Mars

jane.sayGender(); // Jane says my gender is Female
jane.sayPlanet(); // Jane was born on Earth

john.sayGender(); // John says my gender is Female
john.sayPlanet(); // John was born on Earth


delete david.planetOfBirth; //just to show how human properties will still be in the chain even if you delete them
delete john.name; // It's true also if you use new. 
delete jane.sayPlanet;

console.log('\n','----after deleting properties----');

david.sayPlanet();
jane.sayPlanet();
john.sayGender();

human.planetOfBirth = 'Venus'; // This will apply to all humans, even the ones already created
                             
console.log('\n','----after assigning planetOfBirth on human----');

david.sayPlanet();
jane.sayPlanet();
john.sayPlanet(); // John still has planetOfBirth as its own property, since it wasn't deleted

delete john.planetOfBirth;

console.log('\n','----after deleting john planetOfBirth----');

john.sayPlanet();  // But it's still there

var human = {
    planetOfBirth: 'Earth',
    sayGender: function () {
        console.log(this.name + ' says my gender is ' + this.gender);
    },
    sayPlanet: function () {
              console.log(this.name + ' was born on ' + this.planetOfBirth); 
    },
    init: function(name){
        this.name = name;
    }
};

var male = Object.create(human, {
    gender: {value: 'Male'} // This is part of male/female prototype and can't be written, which seems logical
   });

var female = Object.create(human, {
    gender: {value: 'Female'}
});


var david = Object.create(male).init('David');
david.planetOfBirth = 'Mars';

var jane =  Object.create(female).init('Jane')
jane.sayPlanet = function(){console.log('something different')};

var john =  Object.create(male).init('John');
john.planetOfBirth = 'Jupiter';




david.sayGender(); // David says my gender is Male
david.sayPlanet(); // David was born on Mars

jane.sayGender(); // Jane says my gender is Female
jane.sayPlanet(); // Jane was born on Earth

john.sayGender(); // John says my gender is Female
john.sayPlanet(); // John was born on Earth


delete david.planetOfBirth; // Overridden properties will still exists after delete, but not the others.
delete john.name;
delete jane.sayPlanet;

console.log('\n','----after deleting properties----');

david.sayPlanet(); 
jane.sayPlanet(); 
john.sayPlanet(); 

human.planetOfBirth = 'Venus'; // This will apply to all humans, even the ones already created. 
                               // But not for humans woth overridden planetOfBirth.

console.log('\n','----after assigning planetOfBirth on human----');

david.sayPlanet();
jane.sayPlanet();
john.sayPlanet(); // John's name is now undefinded

delete john.planetOfBirth;

console.log('\n','----after deleting john planetOfBirth----');

john.sayPlanet();  //