I want the man object inherits from the person object. I could have done it using the new operator, but it should work with Object.create. But why it is not working? The console.log says undefined instead of the expected hello.
function person() {
this.say="hello";
}
function man() {
this.name="John Miler";
}
man.prototype = Object.create(person);
var Johnny = new man();
console.log(Johnny.say); Your problem is two-fold.
Object.create should be passed the prototype, not the constructor. In this case, you should use Object.create(person.prototype);, not Object.create(person);
The say property is added when the constructor is called, and you never call the parent constructor from the child constructor.
There are a couple ways to solve this, depending on your desired behavior.
call parent constructor.person.call(this);
function person() {
this.say="hello";
}
function man() {
person.call(this);
this.name="John Miler";
}
man.prototype = Object.create(person.prototype);
var Johnny = new man();
console.log(Johnny.say); person.prototype.say = "hello";
function person() {
}
person.prototype.say = "hello";
function man() {
this.name="John Miler";
}
man.prototype = Object.create(person.prototype);
var Johnny = new man();
console.log(Johnny.say); 
instanceof keyword), you would still need to use Object.create in addition to .call. If you don't want the property to change, using a static property is the correct solution. However, if you want it to be dynamic, using .call is the correct solution.If what you try to achieve is for a man object to inherit a person object, try this:
// superclass
function Person() {
this.say = "hello";
}
// superclass method
Person.prototype.doStuff = function() {
console.info('Stuff done.');
};
// subclass
function Man() {
Person.call(this); // call super constructor.
this.name="John Miler";
}
// subclass extends superclass
Man.prototype = Object.create(Person.prototype);
Man.prototype.constructor = Man;
var Johnny = new Man();
console.log(Johnny.say); // hello
Object.create should be passed the prototype not the constructor.
function person() {
this.say="hello";
}
function man() {
this.name="John Miler";
}
man.prototype = Object.create(new person());
var Johnny = new man();
console.log(Johnny.say);
parameterofObject.createshould be prototype, not constructor (as you supplied). Passperson.prototypeinstead ofperson{}or alsonull. All the properties in that object will be inherited, no matter which of the type they are.