creating an object in javascript using arguments

Question

i was reading in a book and here the code is

function Person(name) {

    this.name = name;
}

Person.prototype.legs = 2;

var newperson = new Person("Joe"), prop;


for (prop in newperson) {
    if (newperson.hasOwnProperty(prop)) {
        console.log(prop + ":" + newperson[prop]);

    }

}

I just want to know what is **prop* in this

var newperson = new Person("Joe"), prop;

It is not a argument for sure so what does prop mean here. is it an optional value? thanks

Nicely obfuscated to induce headaches in newbies. Never write code like this, it just causes questions like this. — deceze
– deceze ♦, Commented Sep 29, 2015 at 10:06

Alex · Accepted Answer · 2015-09-29 10:04:31Z

2

var newperson = new Person("Joe"), prop;

is equivalent to

var newperson = new Person("Joe");
var prop;

answered Sep 29, 2015 at 10:04

Alex

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Md. Arafat Al Mahmud · Accepted Answer · 2015-09-29 10:23:21Z

-1

JavaScript follows lexical scoping of variables.

During the compilation phase, JavaScript engine will only catch up the variable declarations.

So, var newperson = new Person("Joe"), prop; after the compilation phase both variables are stored in the scope with no difference. Both are undefined.

At the execution phase, JavaScript will find the initialization of newperson as a Person object. prop is not initialized yet thus undefined.

answered Sep 29, 2015 at 10:23

Md. Arafat Al Mahmud

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