Remove property for all objects in array

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; 
});

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.

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

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

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