[javascript] hasOwnProperty in JavaScript

Consider:

function Shape() {
    this.name = "Generic";
    this.draw = function() {
        return "Drawing " + this.name + " Shape";
    };
}

function welcomeMessage()
{
    var shape1 = new Shape();
    //alert(shape1.draw());
    alert(shape1.hasOwnProperty(name));  // This is returning false
}

.welcomeMessage called on the body.onload event.

I expected shape1.hasOwnProperty(name) to return true, but it's returning false.

What is the correct behavior?

hasOwnProperty() is a nice property to validate object keys. Example:

var obj = {a:1, b:2};

obj.hasOwnProperty('a') // true

Try this:

function welcomeMessage()
{
    var shape1 = new Shape();
    //alert(shape1.draw());
    alert(shape1.hasOwnProperty("name"));
}

When working with reflection in JavaScript, member objects are always refered to as the name as a string. For example:

for(i in obj) { ... }

The loop iterator i will be hold a string value with the name of the property. To use that in code you have to address the property using the array operator like this:

 for(i in obj) {
   alert("The value of obj." + i + " = " + obj[i]);
 }

hasOwnProperty expects the property name as a string, so it would be shape1.hasOwnProperty("name")