Question

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?

Answer 1

hasOwnProperty is a normal JavaScript function that takes a string argument.

When you call shape1.hasOwnProperty(name) you are passing it the value of the name variable (which doesn’t exist), just as it would if you wrote alert(name).

You need to call hasOwnProperty with a string containing name, like this: shape1.hasOwnProperty("name").