Remove property for all objects in array

With ES6, you may deconstruct each object to create new one without named attributes:

const newArray = array.map(({dropAttr1, dropAttr2, ...keepAttrs}) => keepAttrs)

The only other ways are cosmetic and are in fact loops.

For example :

array.forEach(function(v){ delete v.bad });

Notes:

if you want to be compatible with IE8, you'd need a shim for forEach. As you mention prototype, prototype.js also has a shim.
delete is one of the worst "optimization killers". Using it often breaks the performances of your applications. You can't avoid it if you want to really remove a property but you often can either set the property to undefined or just build new objects without the property.

I prefer to use map to delete the property and then return the new array item.

array.map(function(item) { 
    delete item.bad; 
    return item; 
});

Related