Deleting object property from child object , shines the parent property. If you delete it from the top of the prototype chain though , the value of the child object prototype will be undefined.
Mootools 1.4.5, HTML, CSS, JavaScript
Mootools 1.4.2, HTML, CSS, JavaScript
jQuery 1.7, HTML, CSS, JavaScript
jQuery 1.7.1, HTML, CSS, JavaScript