Object.seal Function (JavaScript)

function showSeal() {

    // Create an object that has two properties.
    var obj = { pasta: "spaghetti", length: 10 };

    // Show attributes of the object and its properties.
    showAttributes(obj);

    // Seal the object.
    Object.seal(obj);

    // Show the attributes again.
    showAttributes(obj);

    // Try to add a new property, and then verify that it is
    // not added. It is not added because Object.seal makes the
    // object non-extensible.
    obj.newProp = 50;
    document.write(typeof (obj.newProp) === "undefined");
    document.write(" ");

    // Try to delete a property, and then verify that it is
    // still present. It is not deleted because Object.seal sets
    // the configurable attribute of the property to false.
    delete obj.length;
    document.write(obj.length === 10);
}

function showAttributes(obj) {
    var newLine = "<br />";

    // Show attributes of the object.
    document.write("non-extensible: " + !Object.isExtensible(obj));
    document.write(", isSealed: " + Object.isSealed(obj));
    document.write(", isFrozen: " + Object.isFrozen(obj));
    document.write(newLine);

    // Show attributes of each property.
    for (var prop in obj) {
        var descriptor = Object.getOwnPropertyDescriptor(obj, prop);

        document.write(prop + " - ");
        document.write("configurable: " + descriptor.configurable);
        document.write(", writable: " + descriptor.writable);
        document.write(newLine);
    }
    document.write(newLine);
}

non-extensible: false, isSealed: false, isFrozen: false
pasta - configurable: true, writable: true
length - configurable: true, writable: true

non-extensible: true, isSealed: true, isFrozen: false
pasta - configurable: false, writable: true
length - configurable: false, writable: true

true true