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The only way to remove a property from an object is to use the delete operator. Using null or 0 only removes the value associated with the property but not the key.

The keyword may need to be notated as a string literal in order for it to be properly interpreted by older JavaScript engines.

var test = {
    'case': 'I am a keyword, so I must be notated as a string',
    delete: 'I am a keyword, so me too' // raises SyntaxError
};

Source:JavaScript Garden